在SurfaceView上绘制

1) 背景问题:

根据:

https://developer.android.com/reference/android/view/SurfaceView

要显示的曲面。视图层次结构将负责 与曲面正确合成SurfaceView的任何同级 通常会出现在上面。这可以用来放置 它会对性能产生影响,因为

基于 xav的 Set the Background Image of a SurfaceView

为了更改曲面背景色,可以将一个视图(与曲面视图重叠)放置在surfaceView的顶部,surfaceHolder像素格式为transparent。

2) 奇怪的绘图问题:“线的边缘会自行移动”

纪尧姆亚当

3) 示例:

public class MainActivity extends AppCompatActivity  implements SurfaceHolder.Callback {

private SurfaceView surfaceView;
private View surfaceBackground;
private Button b_change_surface_background_color;
private Button b_clear;
private Path path;
private Paint mPaint = new Paint();
private int[] colors = new int[]{Color.WHITE, Color.GREEN, Color.MAGENTA, Color.BLUE};
private int currentSurfaceBackgroundColor = Color.WHITE;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    b_change_surface_background_color = (Button) findViewById(R.id.b_change_surface_background_color);
    b_change_surface_background_color.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            int colorIndex = new Random().nextInt(colors.length);
            currentSurfaceBackgroundColor = colors[colorIndex];
            changeSurfaceBackgroundColor(currentSurfaceBackgroundColor);
        }
    });

    surfaceView = (SurfaceView) findViewById(R.id.surfaceView);
    surfaceView.setZOrderOnTop(true);
    surfaceView.getHolder().setFormat(PixelFormat.TRANSPARENT);
    surfaceView.getHolder().addCallback(this);

    surfaceBackground = (View) findViewById(R.id.surfaceBackground);

    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.BLACK);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(50);
}

@SuppressLint("ClickableViewAccessibility")
@Override
public void surfaceCreated(SurfaceHolder holder) {
    path = new Path();
    surfaceView.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            float X = event.getX();
            float Y = event.getY();
            switch (event.getActionMasked()) {
                case MotionEvent.ACTION_DOWN:
                    path.reset();
                    path.moveTo(X, Y);
                    break;
                case MotionEvent.ACTION_MOVE:
                    path.lineTo(X, Y);
                    break;
                case MotionEvent.ACTION_UP:
                    path.lineTo(event.getX(),event.getY());
                    Canvas canvas1 = surfaceView.getHolder().lockCanvas();
                    canvas1.drawPath(path, mPaint);
                    surfaceView.getHolder().unlockCanvasAndPost(canvas1);
                    break;

            }
            if(path != null){
                Canvas canvas = surfaceView.getHolder().lockCanvas();
                canvas.drawPath(path, mPaint);
                surfaceView.getHolder().unlockCanvasAndPost(canvas);
            }
            return true;

        }
    });


}

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {

}

private void changeSurfaceBackgroundColor(@ColorInt int color) {
    if (surfaceBackground != null) {
        surfaceBackground.setBackgroundColor(color);
    }
}

}

活动_main.xml文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/rl"
android:layout_width="match_parent"
android:layout_height="match_parent">

<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Change Surface Background Color"
    android:textAllCaps="false"
    android:layout_alignParentTop="true"
    android:id="@+id/b_change_surface_background_color">
</Button>

<SurfaceView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@id/b_change_surface_background_color"
    android:id="@+id/surfaceView">
</SurfaceView>

<View
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/surfaceBackground"
    android:layout_below="@id/b_change_surface_background_color"
    android:background="@android:color/white">
</View>

</RelativeLayout>

4) 输出

Canvas canvas = surfaceHolder.lockCanvas();
canvas.drawPath(path, mPaint);
path.reset(); // move this line out
surfaceHolder.unlockCanvasAndPost(canvas);

试着移动 就在之前 .

path.reset(); // add just above moveTo
path.moveTo(X,Y);

表面视图实际上在你的窗户后面。它在窗户上打了个洞让你看。所以你可以把东西放在你的窗户上面,但是你的窗户后面什么也看不见。所以背景色不起作用。但是你得到的是带有表面视图的画布,所以你可以提供自己的颜色在画布上绘制。

 private void setRefreshColor(){
    Canvas canvas = surfaceHolder.lockCanvas();
    canvas.drawColor(Color.WHITE);
    surfaceHolder.unlockCanvasAndPost(canvas);
}