使用Paint Android在onDraw中绘制透明色

Question

你好我想在画布和油漆的帮助下在位图上绘制颜色。位图上的颜色绘制工作正常，但我想绘制不起作用的透明颜色是我的应用程序绘制黑色，如下

我尝试了一周，但没有成功，我想绘制透明色，如下面

我怎么能这样做有人帮助我 这是我的drawView类

public class DrawView extends View {
public Bitmap mBitmap;
public Canvas mCanvas;
private Path mPath;
private Paint mBitmapPaint;
private Paint mPaint;
private Bitmap imgF;
private static float MIN_ZOOM = 1f;
private static float MAX_ZOOM = 1f;
private float scaleFactor = 1.f;
private ScaleGestureDetector detector;

public DrawView(Context c, AttributeSet attrs) {
    super(c, attrs);
    mPath = new Path();
    mBitmapPaint = new Paint(Paint.DITHER_FLAG);
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setAlpha(200 * 5);
    mPaint.setColor(Color.BLACK);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(9);

}


@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
    mCanvas = new Canvas(mBitmap);
}

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    canvas.save();

    imgF = Bitmap.createScaledBitmap(MainActivity.gImg, canvas.getWidth(),
            canvas.getHeight(), true);
    canvas.drawBitmap(imgF, 0, 0, mBitmapPaint);
    canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
    canvas.drawPath(mPath, mPaint);
    canvas.restore();
   }
}

这是我的XML文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/transparent" <---- transparent background               
     // below the FrameLayout 

android:orientation="vertical" >
<FrameLayout
    android:id="@+id/eraserFrameLayout"
    android:layout_width="fill_parent"
    android:layout_height="0.0dip"
    android:layout_weight="1.0" >

    <com.dxd.bgeraser.DrawView
        android:id="@+id/eraserImageView"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

    <View style="@style/ShadowBarTop" />

    <View style="@style/ShadowBarBottom" />
 </FrameLayout>
</LinearLayout>

Answer 1

确保在保存图像时，压缩格式为 .png

如果

Bitmap.CompressFormat.JPEG 

然后将其替换为

Bitmap.CompressFormat.PNG

Answer 2

透明色码为：＃00000000或您可以使用Color.TRANSPARENT