Android入门

快速上手

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package com.zypc.javaandroiddemo;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Gravity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button=(Button)findViewById(R.id.button); //按钮ID为"button"
        EditText editTextText=(EditText)findViewById(R.id.editTextText); //输入框ID为"editTextText"
        button.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                String gotText=editTextText.getText().toString();
                if(gotText.equals("aaa")){
                    Toast toast=Toast.makeText(MainActivity.this,"Flag正确！", Toast.LENGTH_SHORT);
                    toast.setGravity(Gravity.BOTTOM|Gravity.CENTER,0,0);
                    toast.show();
                }
            }
        });
    }
}

布局基础

XML控制UI界面

在res/layout目录下新建XML布局文件，例如“main_activity.xml”，在Java中这样导入：

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setContentView(R.layout.activity_main);

在布局文件中：

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<FrameLayout ...
	...
	android:background="@mipmap/bg"
    ...
    <TextView
        ...
        android:layout_gravity="center"
        android:text="@string/start"
        android:textSize="18sp"
        android:textColor="#115572" />
</FrameLayout>

再在res/values下的strings.xml中添加字符串常量：

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<?xml ...?>
<resources>
    <string name="app_name">桌面台球</string>
    <string name="start">开始游戏</string>
</resources>

Java控制UI界面

手动用Java新建文本“开始游戏”，点击后出现系统原生提示框，确定进入，退出直接结束程序。

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package com.noname.myapplication;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.graphics.Color;
import android.os.Bundle;
import android.util.Log;
import android.util.TypedValue;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    public TextView text1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        FrameLayout frameLayout=new FrameLayout(this); //创建帧布局管理器
        setContentView(frameLayout); //在Activity中显示frameLayout

        text1=new TextView(this);
        text1.setText("开始游戏");
        text1.setTextSize(TypedValue.COMPLEX_UNIT_SP,18); //可缩放像素18 固定像素为PX
        text1.setTextColor(Color.rgb(17,85,114)); //文字颜色

        FrameLayout.LayoutParams params=new FrameLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,ViewGroup.LayoutParams.WRAP_CONTENT); //创建保存布局参数的对象
        params.gravity= Gravity.CENTER; //居中显示
        text1.setLayoutParams(params); //设置布局参数

        text1.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                new AlertDialog.Builder(MainActivity.this)
                        .setTitle("系统提示")
                        .setMessage("游戏有风险，进入需谨慎，真的要进入吗？")

                        .setPositiveButton("确定",new DialogInterface.OnClickListener(){
                            @Override
                            public void onClick(DialogInterface dialog, int which){
                                Log.i("桌面台球","进入游戏");
                            }
                        })

                        .setNegativeButton("退出",new DialogInterface.OnClickListener(){
                            @Override
                            public void onClick(DialogInterface dialog,int which){
                                Log.i("桌面台球","退出游戏"); //消息日志
                                finish(); //退出程序
                            }
                        })
                        .show();
            }
        });
        frameLayout.addView(text1);//添加到布局管理器中
    }
}

XML与Java混合控制UI界面

做一个3行4列的相册照片列表页面。

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<?xml ... ?>
<GridLayout ...
    xxx
    android:id="@+id/layout"
    ...
    android.orientation="horizontal"
    android.rowCount="3"
    android.columnCount="4"》
</GridLayout>

Java：

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.GridLayout;
import android.widget.ImageView;

public class MainActivity extends AppCompatActivity {

    private ImageView[] img=new ImageView[12];
    private int[] imagePath=new int[]{
            R.mipmap.img01,R.mipmap.img02,R.mipmap.img03,R.mipmap.img04,
            R.mipmap.img05,R.mipmap.img06,R.mipmap.img07,R.mipmap.img08,
            R.mipmap.img09,R.mipmap.img10,R.mipmap.img11,R.mipmap.img12
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        GridLayout layout=(GridLayout)findViewById(R.id.layout);
        for(int i=0;i<imagePath.length;i++){
            img[i]=new ImageView(MainActivity.this);
            img[i].setImageResource(imagePath[i]);
            img[i].setPadding(2,2,2,2);
            ViewGroup.LayoutParams params=new ViewGroup.LayoutParams(116,68);
            img[i].setLayoutParams(params);
            layout.addView(img[i]);
        }
    }
}

自定义View

跟随手指的小兔子。

XML布局：

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<FrameLayout ...
    ...
    android:backgroud="@mipmap/background"
    android:id="@+id/mylayout"
    ...>
</FrameLayout>

Java：

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.FrameLayout;

public class RabbitView extends View {
    public float bitmapX;
    public float bitmapY;
    public RabbitView(Context context){
        super(context);
        bitmapX=290; //默认位置
        bitmapY=130;
    }

    @Override
    protected void onDraw(Canvas canvas){
        super.onDraw(canvas);
        Paint paint=new Paint(); //创建并实例化绘制对象
        Bitmap bitmap= BitmapFactory.decodeResource(this.getResources(),R.mipmap.rabbit); //生成位图对象
        canvas.drawBitmap(bitmap,bitmapX,bitmapY,paint); //绘制小兔子
        if(bitmap.isRecycled()){ //图片是否回收
            bitmap.recycle(); //强制回收
        }
    }
}
public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FrameLayout frameLayout=(FrameLayout)findViewById(R.id.mylayout);
        final RabbitView rabbit=new RabbitView(this);
        rabbit.setOnTouchListener(new View.OnTouchListener(){
            @Override
            public boolean onTouch(View v, MotionEvent event){
                rabbit.bitmapX=event.getX();
                rabbit.bitmapY=event.getY();
                rabbit.invalidate(); //重绘rabbit组件
                return true;
            }
        });
        frameLayout.addView(rabbit); //添加到布局管理器
    }
}

布局管理器

相对布局

XML：

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<RelativeLayout ...
    ...
    android:background="@mipmap/bg"
    ...>
    <TextView
        android:text="发现有Widget的新版本，您想现在就安装吗？"
        android:id="@+id/textView1"
        ...
        android:layout_centerInParent="true"
    />
    <Button
        android:text="以后再说"
        android:id="@_id/button2"
        ...
        android:layout_alignRight="@id/textView1"
        android:layout_below="@id/textView1"
    />
    <Button
        android:text="现在更新"
        android:id="@+id/button1"
        ...
        android:layout_below="@id/textView1"
        android:layout_toLeftOf="@id/button2"
    />
</RelativeLayout>

线性布局

类似微信登陆界面，XML：

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<LinearLayout ...
    ...
    android:orientation="vertical"
    ...>
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="20dp"
        android:hint="QQ号/微信号/Email"
        android:drawableLeft="@mipmap/zhanghao"
    />
    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingBottom="20dp"
        android:hint="密码"
        android:drawableLeft="@mipmap/mima"
    />
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登录"
        android:textColor="#FFFFFF"
        android:background="#FF009688"
    />
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="登录遇到问题？"
        android:gravity="center_horizontal"
        android:paddingTop="20dp"
    />
</LinearLayout>

在AndroidMenifest.xml中application标签修改：

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android:theme="@style/Theme.AppCompat.Light.DarkActionBar"

帧布局

前景图像在右下角，层叠三层正方形，最下层蓝色，然后天蓝色和水蓝色。

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<FrameLayout
    ...
    android:foreground="@mipmap/mr"
    android:foregroundGravity="bottom|right"
    ...
    <TextView
        android:id="@_id/textView1"
        android:layout_width="280dp"
        android:layout_height="280dp"
        android:layout_gravity="center"
        android:background="#FF0000FF"
        android:textColor="#FFFFFF"
        android:text="蓝色背景的TextView"
    />
    <TextView
        android:id="@_id/textView2"
        android:layout_width="230dp"
        android:layout_height="230dp"
        android:layout_gravity="center"
        android:background="#FF0077FF"
        android:textColor="#FFFFFF"
        android:text="天蓝色背景的TextView"
    />
    <TextView
        android:id="@_id/textView3"
        android:layout_width="180dp"
        android:layout_height="180dp"
        android:layout_gravity="center"
        android:background="#FF00B4FF"
        android:textColor="#FFFFFF"
        android:text="水蓝色背景的TextView"
    />
</FrameLayout>

表格布局

从线性布局继承来的，该有的都有。

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<TableLayout
    ...
    android:background="@mipmap/biaoge"
    android:stretchColumns="0,3" 
    ...><!--第1列和第4列允许被拉伸-->
    <!--第一行-->
    <TableRow
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="200dp"
    >
        <TextView/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="18sp"
            android:text="账号："
            android:gravity="center_horizontal"
        />
        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="邮箱或者手机号"
        />
        <TextView/>
    </TableRow>
    <!--第二行-->
    <TableRow
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="200dp"
    >
        ...
    </TableRow>
    ...
</TableLayout>

网格布局

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<GridLayout
    ...
    android:background="@mipmap/bg"
    android:columnCount="6"
    ...><!--共6列-->
    <ImageView
        ...
        android:layout_gravity="end"
        android:layout_columnSpan="4"
        android:layout_column="1"
        android:layout_row="0"
        ...
    /><!--放置在结束位置、占4列、从第2列第1行开始-->
    ...
</GridLayout>

常用UI组件

TextView

略。

EditText

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EditText login=(EditText)findViewById(R.id.login);
String loginText=login.getText().toString();

Button

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Button login=(Button)findViewById(R.id.login);
login.setOnClickListener(new OnClickListener(){
    @Override
    public void onClick(View v){
        //...
    }
})

ImageButton

Java同Button，XML加上：

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<ImageButton
	...
	android:src="@mipmap/play"
>
</ImageButton>

RadioGroup

RadioGroup组件中有若干个RadioButton。

选项改变就触发方法：

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RadioGroup sex=(RadioGroup)findViewById(R.id.radioGroup1);
sex.setOnCheckedChangeListener(new OnCheckedChangeListener(){
    @Override
    public void onCheckedChanged(RadioGroup group,int checkedId){
        RadioButton r=(RadioButton)findViewById(checkedId);
        r.getText(); //获取选中选项的文本
    }
});

选项改变后单击其他元素按钮触发方法：

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final RadioGroup sex=(RadioGroup)findViewById(R.id.radioGroup1);
Button button=(Button)findViewById(R.id.button1);
button.setOnClickListener(new OnClickListener(){
    @Override
    public void onClick(View v){
        for(int i=0;i<sex.getChildCount();i++){
            RadioButton r=(RadioButton)sex.getChildAt(i);
            if(r.isChecked()){
                r.getText();
                break;
            }
        }
    }
});

CheckBox

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final CheckBox like1=(CheckBox)findViewById(R.id.like1);
like1.setOnCheckedChangeListener(new OnCheckedChangeListener(){
    @Override
    public void onCheckedChanged(CompoundButton buttonView,boolean isChecked){
        if(like1.isChecked()){
            like1.getText();
        }
    }
});

DatePicker

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.DatePicker;
import android.widget.Toast;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

    int year,month,day;
    DatePicker datePicker;

    private void show(int year,int monthOfYear,int dayOfMonth){
        String str=year+"年"+monthOfYear+1+"月"+dayOfMonth+"日";
        Toast.makeText(MainActivity.this,str, Toast.LENGTH_SHORT).show();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        datePicker=(DatePicker)findViewById(R.id.datePicker);
        Calendar calendar=Calendar.getInstance();
        year=calendar.get(Calendar.YEAR);
        month=calendar.get(Calendar.MONTH);
        day=calendar.get(Calendar.DAY_OF_MONTH);
        datePicker.init(year,month,day,new DatePicker.OnDateChangedListener(){//获取到的是0~11月，需要+1
            @Override
            public void onDateChanged(DatePicker arg0,int year,int month,int day){
                MainActivity.this.year=year;
                MainActivity.this.month=month;
                MainActivity.this.day=day;
                show(year,month,day);
            }
        });
    }
}

TimePicker

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.TimePicker;
import android.widget.Toast;

import java.util.Calendar;

public class MainActivity extends AppCompatActivity {

    int hour,minute;
    TimePicker timePicker;

    private void show(int hourOfDay,int minute){
        String str=hourOfDay+"时"+minute+"分";
        Toast.makeText(MainActivity.this,str, Toast.LENGTH_SHORT).show();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        timePicker=(TimePicker)findViewById(R.id.timePicker);
        Calendar calendar=Calendar.getInstance();
        hour=calendar.get(Calendar.HOUR_OF_DAY);
        minute=calendar.get(Calendar.MINUTE);
        timePicker.setOnTimeChangedListener(new TimePicker.OnTimeChangedListener(){
            @Override
            public void onTimeChanged(TimePicker view,int hourOfDay,int minute){
                MainActivity.this.hour=hourOfDay;
                MainActivity.this.minute=minute;
                show(hourOfDay,minute);
            }
        });
    }
}

Chronometer

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.SystemClock;
import android.view.WindowManager;
import android.widget.Chronometer;

public class MainActivity extends AppCompatActivity {

    Chronometer ch;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN); //设置全屏

        ch=(Chronometer)findViewById(R.id.ch);
        ch.setBase(SystemClock.elapsedRealtime()); //记录起始时间
        ch.setFormat("%s"); //显示时间格式
        ch.start(); //开启计时器
        ch.setOnChronometerTickListener(new Chronometer.OnChronometerTickListener(){
            @Override
            public void onChronometerTick(Chronometer chronometer){
                if(SystemClock.elapsedRealtime()-ch.getBase()>=60000){
                    ch.stop();
                }
            }
        });
    }
}

ProgressBar

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.View;
import android.view.WindowManager;
import android.widget.ProgressBar;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    private ProgressBar horizonP;
    private int mProgressStatus=0;
    private Handler mHandler; //android.os里的

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

        horizonP=(ProgressBar)findViewById(R.id.progressBar1);
        mHandler=new Handler(){
            @Override
            public void handleMessage(Message msg){
                if(msg.what==0x111){
                    horizonP.setProgress(mProgressStatus);
                }
                else{
                    Toast.makeText(MainActivity.this,"耗时操作已经完成",Toast.LENGTH_SHORT).show();
                    horizonP.setVisibility(View.GONE); //进度条消失
                }
            }
        };

        new Thread(new Runnable(){
            public void run(){
                while(true){
                    mProgressStatus=doWork();
                    Message m=new Message();
                    if(mProgressStatus<100){
                        m.what=0x111;
                        mHandler.sendMessage(m);
                    }
                    else{
                        m.what=0x110;
                        mHandler.sendMessage(m);
                        break;
                    }
                }
            }
            private int doWork(){//模拟耗时操作
                mProgressStatus+=Math.random()*10;
                try{
                    Thread.sleep(200);
                }
                catch(InterruptedException e){
                    e.printStackTrace();
                }
                return mProgressStatus;
            }
        }).start();
    }
}

SeekBar

拖动条。

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.WindowManager;
import android.widget.ImageView;
import android.widget.SeekBar;

public class MainActivity extends AppCompatActivity {

    private ImageView image;
    private SeekBar seekBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

        image=(ImageView)findViewById(R.id.image);
        seekBar=(SeekBar)findViewById(R.id.seekbar);
        seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener(){
            @Override
            public void onProgressChanged(SeekBar arg0,int progress,boolean fromUser){
                image.setImageAlpha(progress); //图像透明度
            }

            @Override
            public void onStartTrackingTouch(SeekBar bar){

            }
            @Override
            public void onStopTrackingTouch(SeekBar bar){
                
            }
        });
    }
}

RatingBar

星级评分条。

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RatingBar;

public class MainActivity extends AppCompatActivity {

    private RatingBar ratingbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ratingbar=(RatingBar)findViewById(R.id.ratingBar1);
        Button button=(Button)findViewById(R.id.btn);
        button.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                int result=ratingbar.getProgress();
                float rating=ratingbar.getRating();
                float step=ratingbar.getStepSize();
                Toast.makeText(MainActivity.this,"你得到了"+rating+"颗星",Toast.LENGTH_SHORT).show();
            }
        });
    }
}

ImageView

原始尺寸：

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<ImageView
    android:src="@mipmap/flower"
    android:id="@+id/imageView2"
    android:maxWidth="90dp"
    android:maxHeight="90dp"
    android:adjustViewBounds="true"
    android:layout_margin="5dp"
    android:layout_height="wrap_content"
    android:layout_width="wrap_content"
/>

限制高度和宽度：

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<ImageView
    ...
    android:adjustViewBound="true"
    ...
/>

保持纵横比缩放图片，并完全显示在ImageView组件右下角：

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<ImageView
    ...
    android:scaleType="fitEnd"
    ...
/>

图像着色为半透明红色：

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<ImageView
    ...
    android:tint="#77FF0000"
    ...
/>

修改AndroidManifest.xml：

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<activity 
    android:name=".MainActivity"
    android:screenOrientation="landscape"
>

ImageSwitcher

图像切换器。

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.WindowManager;
import android.view.animation.AnimationUtils;
import android.widget.ImageSwitcher;
import android.widget.ImageView;
import android.widget.ViewSwitcher;

public class MainActivity extends AppCompatActivity {

    private int[] arrayPictures=new int[]{
            R.mipmap.img01,R.mipmap.img02,R.mipmap.img03,
            R.mipmap.img04,R.mipmap.img05,R.mipmap.img06,
            R.mipmap.img07,R.mipmap.img08,R.mipmap.img09
    };
    private ImageSwitcher imageSwitcher;
    private int pictutureIndex;
    private float touchDownX; //左右滑动时手指按下的X坐标
    private float touchUpX; //抬起的X坐标

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,WindowManager.LayoutParams.FLAG_FULLSCREEN);

        imageSwitcher=(ImageSwitcher)findViewById(R.id.imageswitcher);
        imageSwitcher.setFactory(new ViewSwitcher.ViewFactory(){ //用Factory方法为ImageSwitcher制造ImageView
            @Override
            public View makeView(){
                ImageView imageView=new ImageView(MainActivity.this);
                imageView.setImageResource(arrayPictures[pictutureIndex]);
                return imageView;
            }
        });

        imageSwitcher.setOnTouchListener(new View.OnTouchListener(){
            @Override
            public boolean onTouch(View v, MotionEvent event){
                if(event.getAction()==MotionEvent.ACTION_DOWN){
                    touchDownX=event.getX();
                    return true;
                }
                else if(event.getAction()==MotionEvent.ACTION_UP){
                    touchUpX=event.getX();
                    return true;
                }
                return false;
            }
        });

        if(touchUpX-touchDownX>100){
            pictutureIndex=pictutureIndex==0?arrayPictures.length-1:pictutureIndex-1;
            imageSwitcher.setInAnimation(AnimationUtils.loadAnimation(MainActivity.this,R.anim.slide_in_left));
            imageSwitcher.setOutAnimation(AnimationUtils.loadAnimation(MainActivity.this,R.anim.slide_in_right));
            imageSwitcher.setImageResource(arrayPictures[pictutureIndex]);
        }
    }
}

Spinner

下拉列表框。

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<Spinner
    android:id="@+id/spinner"
    android:entries="@array/ctype"
    ..>
</Spinner>

在res\values\arrays.xml中：

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<?xml ...?>
<resources>
    <string-array name="ctype">
        <item>全部</item>
        <item>电影</item>
        ...
    </string-array>
</resources>

修改AndroidManifest.xml中的application标签：

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android:theme="@style/Theme.AppCompat.Light.DarkActionBar"

Java：

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.Spinner;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Spinner spinner=(Spinner)findViewById(R.id.spinner);
        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener(){
            @Override
            public void onTiemSelected(AdapterView<?>parent, View view, int position, long id){
                String result=parent.getItemAtPosition(position).toString();
                Toast.makeText(MainActivity.this,result,Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onNothingSelected(AdapterView<?>parent){

            }
        });
    }
}

另一种用适配器指定要显示的列表项：

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        String[] ctype=new String[]{"全部","电影",/*...*/};
        ArrayAdapter<String> adapter=new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item,ctype);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        Spinner spinner=(Spinner)findViewById(R.id.spinner1);
        spinner.setAdapter(adapter);
        
        spinner.getSelectedItem();//获取选中值的方法
    }
}

ListView

实现类似微信通讯录朋友列表。

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package com.noname.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ListView listview=(ListView)findViewById(R.id.listview);
        int[] imageId=new int[]{
                R.mipmap.img0, R.mipmap.img1, R.mipmap.img2,
                R.mipmap.img3, R.mipmap.img4, R.mipmap.img5,
                R.mipmap.img6, R.mipmap.img7, R.mipmap.img8
        };
        String[] title=new String[]{"刘一","陈二",/*...*/};

        List<Map<String,Object>> listItems=new ArrayList<Map<String,Object>>();
        for(int i=0;i<imageId.length;i++){
            Map<String,Object>map=new HashMap<String,Object>();
            map.put("image",imageId[i]);
            map.put("名字",title[i]);
            listItems.add(map);
        }
        
        SimpleAdapter adapter=new SimpleAdapter(this,listItems,R.layout.main,new String[]{"名字","image"},new int[]{R.id.title,R.id.image});
        listview.setAdapter(adapter);
        listview.setOnItemClickListener(new AdapterView.OnItemClickListener(){
            @Override
            public void onItemClick(AdapterView<?>parent, View view, int position, long id){
                Map<String,Object>map=(Map<String,Object>)parent.getItemAtPosition(position);
                Toast.makeText(MainActivity.this,map.get("名字").toString(),Toast.LENGTH_SHORT).show();
            }
        });
    }
}