使用Paint Android在onDraw中繪制透明顏色

Question

你好，我想在畫布和繪畫的幫助下在位圖上繪制顏色。 在位圖上進行顏色繪制工作正常，但我想在此處繪制不起作用的透明顏色，這是我的應用程序繪制黑色，如下所示

我從一個星期開始嘗試，但沒有成功，我想繪制透明的顏色，如下所示

我該怎么辦呢有誰在這里幫助我的是我的drawView類

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();
   }
}

這是我的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

確保在保存圖像時壓縮格式為.png

如果

Bitmap.CompressFormat.JPEG 

然后將其替換為

Bitmap.CompressFormat.PNG

Answer 2

透明的顏色代碼是：＃00000000或可以使用Color.TRANSPARENT