Android：撤消，重做操作无法正常工作。

Question

以下是我的代码。我能够画线，但重做和撤消按钮不起作用。请任何人都可以帮忙。

这是我的以下活动。请检查撤销和重做方法...

public class Paint_main extends Activity implements OnTouchListener { 

    static Paint p1; 
    static Paint p2; 
    ImageView img; 
    Bitmap bm; 
    Float startx; 
    Float starty; 
    Float endx; 
    Float endy; 
    Button b1; 
    EditText et; 
    File file; 
    File myDir; 
    private static ToggleButton toggleButton; 
    private Canvas mCanvas; 
    private Path mPath; 

    private ArrayList<Path> paths = new ArrayList<Path>(); 
    private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 
     Button btn_undo = (Button) findViewById(R.id.undoButton); 

     btn_undo.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { onClickUndo(); } 
     }); 

     Button btn_redo = (Button) findViewById(R.id.redoButton); 

     btn_redo.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { onClickRedo(); } 
     }); 

     bm = Bitmap.createBitmap(getWindowManager().getDefaultDisplay().getWidth(), 
           getWindowManager().getDefaultDisplay().getHeight(), 
           Bitmap.Config.ARGB_8888); 

     img = (ImageView) findViewById(R.id.imageView1);  
     img.setImageBitmap(bm); 

     p1 = new Paint(); 
     p1.setAntiAlias(true); 
     p1.setDither(true); 
     p1.setStyle(Paint.Style.STROKE); 
     p1.setStrokeJoin(Paint.Join.ROUND); 
     p1.setStrokeCap(Paint.Cap.ROUND); 
     p1.setColor(Color.GREEN); 
     p1.setStrokeWidth(6); 
     mCanvas = new Canvas(bm); 
     mPath = new Path(); 
     // paths.add(mPath); 
     img.setOnTouchListener(this); 
    } 

    private float mX, mY; 
    private static final float TOUCH_TOLERANCE = 4; 

    private void touch_start(float x, float y) { 
     mPath.reset(); 
     mPath.moveTo(x, y); 
     mX = x; 
     mY = y; 
    } 

    private void touch_move(float x, float y) { 
     float dx = Math.abs(x - mX); 
     float dy = Math.abs(y - mY); 

     if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) { 
      mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 
      mX = x; 
      mY = y; 
     } 
    } 

    private void touch_up() { 
     mPath.lineTo(mX, mY); 
     // commit the path to our offscreen 
     mCanvas.drawPath(mPath, p1); 
     // kill this so we don't double draw    
     // mPath = new Path(); 
     // paths.add(mPath); 
     paths.add(mPath); 
     mPath = new Path(); 
    } 

    public void onClickUndo() { 
     if (paths.size() > 0) { 
      undonePaths.add(paths.remove(paths.size()-1)); 
      img.invalidate(); 
      onDraw(mCanvas); 
     } 
    } 

    public void onClickRedo(){ 
     if (undonePaths.size() > 0) { 
      paths.add(undonePaths.remove(undonePaths.size()-1)); 
      img.invalidate(); 
      onDraw(mCanvas); 
     } 
    } 


    public boolean onTouch(View arg0, MotionEvent event) { 
     float x = event.getX(); 
     float y = event.getY(); 

     switch (event.getAction()) { 
      case MotionEvent.ACTION_DOWN: 
       touch_start(x, y); 
       img.invalidate(); 
       onDraw(mCanvas); 
       break; 
      case MotionEvent.ACTION_MOVE: 
       touch_move(x, y); 
       img.invalidate(); 
       onDraw(mCanvas); 
       break; 
      case MotionEvent.ACTION_UP: 
       touch_up(); 
       img.invalidate(); 
       onDraw(mCanvas); 
       break; 
     } 
     return true; 
    } 

    protected void onDraw(Canvas canvas) { 
     //mPath = new Path(); 
     //canvas.drawPath(mPath, mPaint); 

     for (Path p : paths) { canvas.drawPath(p, p1); } 
     canvas.drawPath(mPath, p1); 
    } 
} 

可能是我错误地调用上述onDraw方法。

Answer 1

我明白了。问题是：img.setOnTouchListener(this);这会得到事件，处理它并返回true，这意味着这个事件是handlet。

你有3种选择：

1）设置onTouchListener到父视图并手动发送触摸事件童车 2）你可以判断用户的触摸图像return true，否则返回false 3）写自己的类和覆盖onTouchEvent(..)方法

我推荐3个选项。我重写你：

package com.example.paint_main; 

import java.io.File; 
import java.util.ArrayList; 

import android.app.Activity; 
import android.content.Context; 
import android.graphics.Bitmap; 
import android.graphics.Canvas; 
import android.graphics.Color; 
import android.graphics.Paint; 
import android.graphics.Path; 
import android.os.Bundle; 
import android.util.AttributeSet; 
import android.view.MotionEvent; 
import android.view.View; 
import android.view.View.OnClickListener; 
import android.view.View.OnTouchListener; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.ImageView; 
import android.widget.ToggleButton; 

public class Paint_main extends Activity { 

    MyImageView img; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_paint_main); 

     img = (MyImageView) findViewById(R.id.imageView1); 
     img.init(getWindowManager().getDefaultDisplay().getWidth(), getWindowManager().getDefaultDisplay().getHeight()); 

     Button btn_undo = (Button) findViewById(R.id.undoButton); 

     btn_undo.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { img.onClickUndo(); } 
     }); 

     Button btn_redo = (Button) findViewById(R.id.redoButton); 

     btn_redo.setOnClickListener(new OnClickListener() { 
      @Override 
      public void onClick(View v) { img.onClickRedo(); } 
     }); 
    } 

    static class MyImageView extends ImageView { 

     static Paint p1; 
     static Paint p2; 
     Bitmap bm = null; 
     Float startx; 
     Float starty; 
     Float endx; 
     Float endy; 
     Button b1; 
     EditText et; 
     File file; 
     File myDir; 
     private static ToggleButton toggleButton; 
     private Canvas mCanvas; 
     private Path mPath; 

     private ArrayList<Path> paths = new ArrayList<Path>(); 
     private ArrayList<Path> undonePaths = new ArrayList<Path>(); 

     static { 
      p1 = new Paint(); 
      p1.setAntiAlias(true); 
      p1.setDither(true); 
      p1.setStyle(Paint.Style.STROKE); 
      p1.setStrokeJoin(Paint.Join.ROUND); 
      p1.setStrokeCap(Paint.Cap.ROUND); 
      p1.setColor(Color.GREEN); 
      p1.setStrokeWidth(6); 
     } 

     public MyImageView(Context context, AttributeSet attrs, int defStyle) { 
      super(context, attrs, defStyle); 
     } 

     public MyImageView(Context context, AttributeSet attrs) { 
      super(context, attrs); 
     } 

     public MyImageView(Context context) { 
      super(context); 
     } 

     public void init(int width, int height) { 
      bm = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888); 
      mCanvas = new Canvas(bm); 
      mPath = new Path(); 
     } 

     @Override 
     public boolean onTouchEvent(MotionEvent event) { 
      float x = event.getX(); 
      float y = event.getY(); 

      switch (event.getAction()) { 
       case MotionEvent.ACTION_DOWN: 
        touch_start(x, y); 
        this.invalidate(); 
        onDraw(mCanvas); 
        break; 
       case MotionEvent.ACTION_MOVE: 
        touch_move(x, y); 
        this.invalidate(); 
        onDraw(mCanvas); 
        break; 
       case MotionEvent.ACTION_UP: 
        touch_up(); 
        this.invalidate(); 
        onDraw(mCanvas); 
        break; 
      } 
      return true; 
     } 

     private float mX, mY; 
     private static final float TOUCH_TOLERANCE = 4; 

     private void touch_start(float x, float y) { 
      mPath.reset(); 
      mPath.moveTo(x, y); 
      mX = x; 
      mY = y; 
     } 

     private void touch_move(float x, float y) { 
      float dx = Math.abs(x - mX); 
      float dy = Math.abs(y - mY); 

      if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) { 
       mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2); 
       mX = x; 
       mY = y; 
      } 
     } 

     private void touch_up() { 
      mPath.lineTo(mX, mY); 
      // commit the path to our offscreen 
      mCanvas.drawPath(mPath, p1); 
      // kill this so we don't double draw    
      // mPath = new Path(); 
      // paths.add(mPath); 
      paths.add(mPath); 
      mPath = new Path(); 
     } 

     public void onClickUndo() { 
      if (paths.size() > 0) { 
       undonePaths.add(paths.remove(paths.size()-1)); 
       invalidate(); 
       onDraw(mCanvas); 
      } 
     } 

     public void onClickRedo(){ 
      if (undonePaths.size() > 0) { 
       paths.add(undonePaths.remove(undonePaths.size()-1)); 
       invalidate(); 
       onDraw(mCanvas); 
      } 
     } 

     protected void onDraw(Canvas canvas) { 
      //mPath = new Path(); 
      //canvas.drawPath(mPath, mPaint); 

      if (bm == null) 
       return; 

      for (Path p : paths) { 
       canvas.drawPath(p, p1); } 
       canvas.drawPath(mPath, p1); 
     } 
    } 
} 

不要忘记添加你的类到布局：

<view class="com.example.paint_main.Paint_main$MyImageView" 
    android:id="@+id/imageView1" 
    android:layout_width="wrap_content" 
    android:layout_height="wrap_content" 
    android:layout_above="@+id/redoButton" 
    android:layout_alignParentLeft="true" 
    android:layout_alignParentRight="true" 
    android:layout_alignParentTop="true" /> 

此外，你应该使用视图代替ImageView的，因为你不使用任何特定的ImageView的功能。我用ImageView重写更容易理解我的意思是第三种选择。