下面是我的 Android 新画家应用程序。
但是，它不反映以前绘制的对象。 （当我触摸屏幕时，它失去了形状）
为了反映以前绘制的对象，我尝试使用“Bitmap.createBitmap”方法但它不起作用。
请帮助我。
public class CreativePainterActivity extends Activity {
//
//private MyView vw;
Paint mPaint;
//--Variables to store the current figure info
private float _currentStartX; //where mouse first pressed
private float _currentStartY;
private float _currentEndX; //where dragged to or released
private float _currentEndY;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
setContentView(new MyView(this));
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setDither(true);
mPaint.setColor(0xFFFFFF00);
mPaint.setStyle(Paint.Style.STROKE);
mPaint.setStrokeJoin(Paint.Join.ROUND);
mPaint.setStrokeCap(Paint.Cap.ROUND);
mPaint.setStrokeWidth(8);
}
//view class
public class MyView extends View{
private Canvas mCanvas;
private Bitmap mBitmap;
private Paint mBitmapPaint;
Bitmap bm;
//private Paint mBitmapPaint;
public MyView(Context context){
super(context);
//ADDED
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
mBitmap = Bitmap.createBitmap(metrics.widthPixels, metrics.heightPixels, Bitmap.Config.ARGB_8888);
mCanvas = new Canvas(mBitmap);
mBitmapPaint = new Paint(Paint.DITHER_FLAG);
mCanvas.drawColor(0xFFFFFFFF);
bm = BitmapFactory.decodeResource(getResources(),R.drawable.ic_launcher);
}
public void onDraw(Canvas canvas){
//canvas.drawColor(Color.LTGRAY);
canvas.drawBitmap(bm, 0, 0, mBitmapPaint);
canvas.drawLine(_currentStartX, _currentStartY, _currentEndX, _currentEndY, mPaint);
}
//Methods for touch events
public boolean onTouchEvent(MotionEvent event){
if (event.getAction() == MotionEvent.ACTION_DOWN){
_currentStartX=event.getX();
_currentStartY=event.getY();
return true;
}
if(event.getAction() == MotionEvent.ACTION_MOVE){
_currentEndX=event.getX();
_currentEndY=event.getY();
invalidate();
return true;
}
return true;
}
}//end of the class MyView
}//end of the class CreativePainterActivity
你需要更多地了解视图是如何绘制的。再次绘制后，您的视图将不会保留其中的任何内容。所以，你应该以某种方式保存以前的任何东西，并重绘旧的东西，以及新的变化。
一个更简单的解决方案，将以前的绘图保存到位图，然后先在画布上再次绘制该位图，并添加新内容。
流量
onDraw(){
绘制位图（bmp）；
绘制其他东西（）；
bmp = saveOnScreenBitmap();
}
所以，每次都需要保存上次绘制的位图，重新绘制。希望现在更清楚了。