Android SurfaceView预览变形完美解决

转载请注明出处：https://www.jianshu.com/p/0ea58e77ef57
这个问题百度上一搜一大把，基本上都是说找到和SurfaceView的比例相近的camera预览尺寸，但是发现预览时候还是差了点意思，具体看下面这个回调就知道是为什么了。

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        Log.i(TAG, "surfaceChanged: " + width + "  " + height);
    }

从上面的回调打印的数据知道surfaceview的宽高比可能与camera设置的宽高比不一致，其实取相近的比例解决不了根本问题。
所以，对于此类的解决方法我只想说仅仅相近有神马用。

那么既然知道surfaceChanged的宽高就是SurfaceView的渲染宽高，那么想办法把surfaceChanged里的宽高比弄成和camera比例一样不就行了嘛，所以看SurfaceView的源码：

protected void updateWindow(boolean force, boolean redrawNeeded) {
        ...代码省略

        int myWidth = mRequestedWidth;
        if (myWidth <= 0) myWidth = getWidth();
        int myHeight = mRequestedHeight;
        if (myHeight <= 0) myHeight = getHeight();

        ...代码省略
            
        if (creating || formatChanged || sizeChanged
                || visibleChanged || realSizeChanged) {
            if (DEBUG) Log.i(TAG, System.identityHashCode(this) + " "
                    + "surfaceChanged -- format=" + mFormat
                    + " w=" + myWidth + " h=" + myHeight);
            if (callbacks == null) {
                callbacks = getSurfaceCallbacks();
            }
            for (SurfaceHolder.Callback c : callbacks) {
                c.surfaceChanged(mSurfaceHolder, mFormat, myWidth, myHeight);
            }
        }
        
        ...代码省略
    }

可以看到宽高其实就是调用的View的getHeight和getWidth或者是mRequestedWidth和mRequestedHeight。
熟悉了View的自定义就知道getHeight和getWidth都是和View的onMeasure息息相关，所以想到重写onMeasure方法。
再从源码看到关于mRequestedWidth和mRequestedHeight的赋值

@Override
        public void setFixedSize(int width, int height) {
            if (mRequestedWidth != width || mRequestedHeight != height) {
                mRequestedWidth = width;
                mRequestedHeight = height;
                requestLayout();
            }
        }

以下是完整类代码：

public class ResizeAbleSurfaceView extends SurfaceView {

    private int mWidth = -1;
    private int mHeight = -1;

    public ResizeAbleSurfaceView(Context context) {
        super(context);
    }

    public ResizeAbleSurfaceView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public ResizeAbleSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        if (-1 == mWidth || -1 == mHeight) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        } else {
            setMeasuredDimension(mWidth, mHeight);
        }
    }

    public void resize(int width, int height) {
        mWidth = width;
        mHeight = height;
        getHolder().setFixedSize(width, height);
        requestLayout();
        invalidate(); 
    }
}

实例化的时候记得调用resize方法就好了。
注意和camera的预览尺寸比例一致，且宽高记得传正确，不然可能不全屏