我正在开发一个android绘图应用程序。当我运行这个代码时，它说应用程序在logcat的主线程上做了太多的工作。我不能绘图。请帮助我。谢谢
这是我的绘画课

public class Drawit extends Activity  {
LinearLayout linearLayout;
ImageButton oclear,save,ocancel;
View mview;
DrawCanvas drawCanvas;

public static String tempDir;
public static String unique_id;
public static String current=null;
public Bitmap mBitmap;
public EditText yourName;
File  myPath;
protected void onCreate(Bundle savedInsatnceState)  {
        // TODO Auto-generated method stub
        super.onCreate(savedInsatnceState);
        setContentView(R.layout.drawit);

        linearLayout  = (LinearLayout) findViewById(R.id.linearLayout11);
        tempDir = Environment.getExternalStorageDirectory()+"/"+getResources().getString(R.string.external_dir);
        ContextWrapper contextWrapper = new ContextWrapper(getApplicationContext());
        File directory= contextWrapper.getDir(getResources().getString(R.string.external_dir),MODE_PRIVATE);
        preparedirectory();
        yourName = (EditText) findViewById(R.id.editText1);

        myPath = new File(directory,current);

    drawCanvas = new DrawCanvas(this, null);
    drawCanvas.setBackgroundColor(Color.WHITE);

    linearLayout.addView(drawCanvas,LayoutParams.FILL_PARENT);

}
}

这是我画画布的方法

public class DrawCanvas extends View 
 {
public Paint paint = new Paint();
public Path path = new Path();
public final RectF dirtyRect = new RectF();
public float lastTouchX;
public float lastTouchY;

public DrawCanvas(Context context, AttributeSet attrs) {
    super(context, attrs);
    // TODO Auto-generated constructor stub
    paint.setColor(Color.BLACK);
    paint.setStrokeWidth(5f);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setStrokeJoin(Paint.Join.ROUND);
    paint.setAntiAlias(true);
}

protected void ondraw(Canvas canvas) {
    canvas.drawPath(path,paint);

}

public void save(View mview) throws IOException{
    // TODO Auto-generated method stub

    if(mBitmap == null)
    {
        mBitmap = Bitmap.createBitmap(linearLayout.getWidth(),linearLayout.getHeight(),Bitmap.Config.RGB_565);
    }
    Canvas canvas = new Canvas(mBitmap);
    try {
        FileOutputStream fileoutputstream = new FileOutputStream(myPath);
        mview.draw(canvas);

        mBitmap.compress(Bitmap.CompressFormat.PNG , 90, fileoutputstream);
        fileoutputstream.flush();
        fileoutputstream.close();

        String uri = Images.Media.insertImage(getContentResolver(),mBitmap,"title",null);
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } 

}   

public void clear() {
    // TODO Auto-generated method stub
    path.reset();
    invalidate();
    }

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

    switch(event.getAction())
    {
    case MotionEvent.ACTION_DOWN:
        path.moveTo(eventX, eventY);
        lastTouchX = eventX;
        lastTouchY = eventY;
        return true;

    case MotionEvent.ACTION_MOVE:

    case MotionEvent.ACTION_UP:
        resetDirtyRect(eventX,eventY);
        int historyRectSize = event.getHistorySize();
        for(int i=0;i<historyRectSize;i++)
        {
            float historicalx = event.getHistoricalX(i);
            float historicaly = event.getHistoricalY(i);
            expandDirtyRect(historicalx,historicaly);
            path.lineTo(historicalx, historicaly);
        }

        break;

    }
    return true;

}
private void expandDirtyRect(float historicalx, float historicaly) {
    // TODO Auto-generated method stub
    if(historicalx < dirtyRect.left)
    {
        dirtyRect.left = historicalx;
    } else if(historicalx >dirtyRect.right)
    {
        dirtyRect.left = historicalx;
    }

    if(historicaly < dirtyRect.top)
    {
        dirtyRect.top = historicaly;
    } else if(historicaly >dirtyRect.bottom)
    {
        dirtyRect.bottom = historicaly;
    }
}

private void resetDirtyRect(float eventX, float eventY) {
    // TODO Auto-generated method stub
    dirtyRect.left =  Math.min(lastTouchX,eventX);
    dirtyRect.right =  Math.max(lastTouchX,eventX);
    dirtyRect.top =  Math.min(lastTouchY,eventY);
    dirtyRect.bottom =  Math.max(lastTouchY,eventY);

}

} 
}