光栅化后应用Android设备上查看转换？ [英] Are Android View transformations applied after rasterization?

问题描述

在code中的线（A）和线（b）所示应该产生同样的图像。

The lines (A) and the lines (B) in the code below should produce the same image.

然而，线（A）产生，而不是图片：

Yet lines (A) produce instead the image:

这是怎么回事？光栅化后应用查看/帆布转变？

What is happening? Are View/Canvas transformations applied after rasterization?

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.RectF;
import android.view.View;
import android.graphics.Matrix;

public class MyView extends View {
    Paint paint = new Paint();

    public MyView(Context c) {
        super(c);
        // this.setLayerType(View.LAYER_TYPE_SOFTWARE, null); // (C)
    }

    Rect canvasRect   = new Rect();
    RectF canvasRectf = new RectF();
    RectF scene = new RectF();
    Matrix M = new Matrix();

    @Override
    protected void onDraw(Canvas canvas) {
        getDrawingRect(canvasRect);
        canvasRectf.set(canvasRect);

        scene.set(0,0, 100,100); // (A)
        // scene.set(0,0, 500,500); // (B)

        M.setRectToRect(scene, canvasRectf, Matrix.ScaleToFit.CENTER);
        canvas.setMatrix(M);

        canvas.drawCircle( 50, 50, 1, paint); // (A)
        // canvas.drawCircle(250,250, 5, paint); // (B)
    }
}

更新：如果线（C）是注释掉，问题就不会出现（感谢，亨利）。是否有可能在使用硬件加速来获得的第一个形象呢？

Update: If line (C) is uncommented, the problem does not arise (Thanks, Henry). Is it possible to get the first image while using hardware acceleration?

推荐答案

启用硬件加速时，我只能采用Android 4.1.2重现该问题。难道是一个错误吗？

I could reproduce the problem only with Android 4.1.2 when hardware acceleration is enabled. Could it be a bug?

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