canvas.drawLine（）沒有出現在位圖上

我已經嘗試了很多方法，但我的代碼仍拒絕在畫布上簡單地畫一條線。我已經註釋過的每個嘗試都會使程序崩潰或不顯示該行。我真的很努力地想知道如何做到這一點，我不斷得到有關使用線程或onDraw或其他方面的不同建議，但似乎沒有任何工作。canvas.drawLine（）沒有出現在位圖上

我的總體目標是在屏幕上顯示位圖圖像，並在其上畫線。然後我希望使用canvas.tranlate使整個圖像（位圖及其頂部的線）可以進行泛像化。（我已經實現的功能，成功平移圖像。）

public class Main extends Activity implements OnTouchListener { 
CanvasView myCanvas; 
Canvas canvas; 
Bitmap bmp; 
float fingerPosX = 0; 
float fingerPosY = 0; 
float preFingerPosX = 0; 
float preFingerPosY = 0; 
float bmpX = 0; 
float bmpY = 0; 
float dx = 0; 
float dy = 0; 
Paint paint; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    bmp = BitmapFactory.decodeResource(getResources(), R.drawable.gmit2013mod); 
    canvas = new Canvas(); 
    myCanvas = new CanvasView(this); 
    myCanvas.setOnTouchListener(this); 
    setContentView(myCanvas); 

} 

@Override 
public void onPause() { 
    super.onPause(); 
    myCanvas.pause(); 
} 

@Override 
public void onResume() { 
    super.onResume(); 
    myCanvas.resume(); 
} 

public boolean onTouch(View v, MotionEvent event) { 
    int action = event.getAction(); 
    if(action == event.ACTION_DOWN) {  //when touch is received get finger position 
     preFingerPosX = event.getX(); 
     preFingerPosY = event.getY(); 
    } 

    if(action == event.ACTION_UP) {   //when touch is released get finger position 
     fingerPosX = event.getX(); 
     fingerPosY = event.getY(); 
     dx = fingerPosX - preFingerPosX; //subtract previous finger position from current 
     dy = fingerPosY - preFingerPosY; 
     bmpX += dx;       //apply difference to image 
     bmpY += dy; 
    } 
    //CanvasView.updateMap(); 
    //invalidate(); 

    return true; 
} 

//CanvasView Class 
public class CanvasView extends SurfaceView implements Runnable{ //implements Runnable 
    SurfaceHolder surfaceHolder; 
    Thread myThread = null; 
    boolean isRunning = false; 

    public CanvasView(Context context) { 
     super(context); 
     surfaceHolder = getHolder(); 
    } 

    @Override 
    protected void onDraw(Canvas canvas) { 
     super.onDraw(canvas); 
    // canvas.drawBitmap(bmp, 0, 0, null); 
     //canvas = surfaceHolder.lockCanvas(); 
     canvas.drawLine(10, 10, 30, 30, paint); 
     //surfaceHolder.unlockCanvasAndPost(canvas); 
    } 

    public void pause() { 
     isRunning = false; 
     while(true) { 
      try { 
       myThread.join(); 
      } 
      catch (InterruptedException e) { 
       e.printStackTrace(); 
      } 
      break; 
     } 
     myThread = null; 
    } 

    public void resume() { 
     isRunning = true; 
     myThread = new Thread(this); 
     myThread.start(); 
    } 

    public void run() { 
     while(isRunning) { 
      //init(); //crashes when code here 
      if(!surfaceHolder.getSurface().isValid()) { 
       continue; 
      } 
      invalidate(); 
      //init(); 
      //canvas.translate(bmpX, bmpY); 
      updateMap(); 
      //invalidate(); 
     } 
    } 

    // canvas = surfaceHolder.lockCanvas(); 
    // canvas.drawRGB(255, 255, 255); 
    // canvas.drawBitmap(bmp, 0-(bmp.getWidth()/2), 0-(bmp.getHeight()/2), null); 
    // surfaceHolder.unlockCanvasAndPost(canvas); 
    } 

    public void updateMap() { 
     runOnUiThread(new Runnable() { 

      public void run() { 
       // TODO Auto-generated method stub 
       //canvas = surfaceHolder.lockCanvas(); 
       //canvas.drawRGB(255, 255, 255); 
       //canvas.drawBitmap(bmp, bmpX-(bmp.getWidth()/2), bmpY-(bmp.getHeight()/2), null); 
       //paint.setColor(Color.RED); 
       //canvas.drawLine(10, 10, 30, 30, paint); //it seems this must b in ondraw. try canvas(bmp) again, mite have some affect with different bmp 
       //invalidate(); 
       //surfaceHolder.unlockCanvasAndPost(canvas); 

      } 

     }); 
    } 
}

這裏是我的代碼，如果你能爲我提供任何解決方案或已聯機工作的一些這方面的例子，因爲我跑出來我將不勝感激在這個項目上的時間！由於

UPDATE： 我添加下面的代碼行到onCreate方法：

Drawable drawBmp = new BitmapDrawable(bmp); 
drawBmp.draw(canvas);

來源

2013-04-17 logicalfox

看看這個鏈接... [這裏] [1] [1]：http://stackoverflow.com/questions/14427665/android-drawing-app-line-cannot在畫廊上繪製的位圖加載 – AndiM

我需要在添加的onCreate paint = new Paint()。油漆對象是null所以這就是爲什麼它不會畫。花了我幾周的時間和一個荒謬的糾纏只是爲了發現！我正在度假......

如果有人打算製作這樣的項目，我打算在不久的將來製作一些YouTube視頻教程，以幫助任何人落入我所做的同樣愚蠢的陷阱！

非常感謝user_CC，他的所有時間和幫助解決了這個問題！

來源

2013-04-23 12:04:00 logicalfox

您需要創建位圖作爲Drawble對象，然後在該位圖繪製不是畫布上它自我。

因此，基本上你可以在BitmapFactory選項幫助下創建的Bitmap對象的幫助下創建一個BitmapDrawable對象。您將不得不使用此Drawable類的draw（Canvas c）方法在位圖上繪製。

http://developer.android.com/reference/android/graphics/drawable/BitmapDrawable.html

來源

2013-04-17 11:28:34

好吧我想我明白了，我會非常感謝！ – logicalfox

好聽，讓我知道你如何得到 –

'BitmapDrawable drawBmp; – logicalfox

canvas.drawLine（）沒有出現在位圖上

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