<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools" android:id="@+id/activity_main"
  android:layout_width="match_parent" android:layout_height="match_parent"
  tools:context="com.example.demo.MainActivity">

  <ImageView
    android:id="@+id/iv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/bg"
    />

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:layout_alignParentBottom="true"
    >
    <Button
      android:id="@+id/red"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="紅色"
      android:onClick="onplay"
      />
    <Button
      android:id="@+id/green"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="綠色"
      android:onClick="onplay"
      />
    <Button
      android:id="@+id/root"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="刷子"
      android:onClick="onplay"
      />
    <Button
      android:id="@+id/save"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="保存"
      android:onClick="onplay"
      />
    <Button
      android:id="@+id/finish"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:text="涂漆"
      android:onClick="onplay"
      />
  </LinearLayout>

</RelativeLayout>

/*
畫(huà)板canvas  畫(huà)板paint 手勢(shì)識(shí)別器
整體思路:因?yàn)槲沂菆D片是作畫(huà),實(shí)際是對(duì)圖片進(jìn)行修改,起到畫(huà)圖的效果
1.原圖,白紙,畫(huà)筆,畫(huà)板
2.根據(jù)手勢(shì)識(shí)別進(jìn)行作畫(huà)

 */
public class MainActivity extends AppCompatActivity {
private Bitmap bitmap;
  private Canvas canvas;
private ImageView iv;
  private int startx;
  private int starty;
  private Paint paint;
  private Bitmap bmSrc;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //加載原圖
    bmSrc = BitmapFactory.decodeResource(getResources(), R.drawable.bg);
    //創(chuàng)建白紙,寬,高,圖片的參數(shù)
     bitmap = Bitmap.createBitmap(bmSrc.getWidth(), bmSrc.getHeight(), bmSrc.getConfig());
    //創(chuàng)建畫(huà)板,參數(shù)是白紙對(duì)象
    canvas = new Canvas(bitmap);
    //創(chuàng)建畫(huà)筆
    paint = new Paint();
    //在紙上作畫(huà)
    iv=(ImageView)findViewById(R.id.iv);
    canvas.drawBitmap(bmSrc,new Matrix(), paint);
    //-----------------手勢(shì)識(shí)別器和畫(huà)筆結(jié)合的知識(shí)-------------------
  //給控件設(shè)置手勢(shì)適配器,可以得到用戶(hù)在這個(gè)控件上所做的手勢(shì)
    iv.setOnTouchListener(new View.OnTouchListener() {


      //當(dāng)用戶(hù)手在這個(gè)控件時(shí),指的就是用戶(hù)的手對(duì)控件滑動(dòng),按下,松開(kāi)的三種場(chǎng)景,自動(dòng)回調(diào)
      @Override
      public boolean onTouch(View view, MotionEvent motionEvent) {
        switch (motionEvent.getAction()){
          case MotionEvent.ACTION_DOWN://按下時(shí)回調(diào)一次
            //獲取用戶(hù)手指按下時(shí)的坐標(biāo)
            startx = (int) motionEvent.getX();
            starty = (int) motionEvent.getY();
            break;
          case MotionEvent.ACTION_MOVE://手指滑動(dòng)時(shí),不停地調(diào)用
            int newx = (int) motionEvent.getX();
            int newy = (int) motionEvent.getY();
            //在背景圖畫(huà)線
            canvas.drawLine(startx,starty,newx,newy, paint);
            startx=newx;
            starty=newy;
            iv.setImageBitmap(bitmap);
            break;
          case MotionEvent.ACTION_UP://松開(kāi)時(shí)回調(diào)一次

            break;
        }
        //事情分發(fā)機(jī)制
        //true:iv處理該觸摸事件
        //false:iv不處理該觸摸事件,事件傳遞給上一級(jí)
        return true;
      }
    });
  }
  public void onplay(View view){
   switch (view.getId()){
     case R.id.red:
       paint.setColor(Color.RED);
       break;
     case R.id.green:
       paint.setColor(Color.GREEN);
       break;
     case R.id.root:
       paint.setStrokeWidth(5);
       break;
     case R.id.save:
       if(SaveViewUtil.saveScreen(iv)){
         Toast.makeText(this, "截圖成功", Toast.LENGTH_SHORT).show();
       }else{
         Toast.makeText(this, "截圖失敗，請(qǐng)檢查sdcard是否可用", Toast.LENGTH_SHORT).show();
       }
       break;
     //涂漆
     case R.id.finish:
       canvas.drawRect(new Rect(0,0,width,height), paint);
       break;
     }

   }
  }

public class SaveViewUtil {
  
  private static final File rootDir = new File(Environment.getExternalStorageDirectory()+File.separator);

  /**保存截圖的方法*/
  public static boolean saveScreen(View view){
   //判斷sdcard是否可用
   if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
     return false;
   }
   if(!rootDir.exists()){
     rootDir.mkdir();
   }
   view.setDrawingCacheEnabled(true);
   view.buildDrawingCache();
   Bitmap bitmap = view.getDrawingCache();
   try {
     bitmap.compress(CompressFormat.JPEG, 100, new FileOutputStream(new File(rootDir,System.currentTimeMillis()+".jpg")));
     return true;
   } catch (FileNotFoundException e) {
     e.printStackTrace();
     return false;
   }finally{
     view.setDrawingCacheEnabled(false);
     bitmap = null;
   }
  }
}
<!-- 往SDCard寫(xiě)入數(shù)據(jù)權(quán)限 -->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>