Android PhotoView 在方向改变后保持缩放

Question

我正在使用 PhotoView Chris Banes 的类(class)能够放大图像并查看它，但我想做到这一点，以便当我改变方向时，照片在改变后仍会被放大。

我了解如何执行此操作的基础知识，当检测到方向更改时，将调用 onSaveInstanceState，因此我尝试将实例保存在那里，然后在调用 onCreate 时将其放回 PhotoView .

public class MainActivity extends ActionBarActivity
{
PhotoView mPhotoView;

@Override
protected void onCreate( Bundle aSavedInstanceState )
{
    super.onCreate( aSavedInstanceState );

    mPhotoView = new PhotoView(this);
    mPhotoView.setMaximumScale( 12 );
    setContentView( mPhotoView );
    mPhotoView.setImageResource( R.drawable.vm_app_icon);

    if (aSavedInstanceState != null)
    {
        RectF theRect = aSavedInstanceState.getParcelable( "Rect" );
        if ( theRect != null)
        {
            Matrix theMatrix = new Matrix();
            theMatrix.setScale( theRect.bottom, theRect.left, theRect.right, theRect.top );
            mPhotoView.setDisplayMatrix( theMatrix );

        }
    }
}

@Override
protected void onSaveInstanceState( final Bundle outState )
{
    super.onSaveInstanceState( outState );
    RectF theRect = mPhotoView.getDisplayRect();
    if (theRect != null)
    {
        outState.putParcelable( "Rect", theRect );
    }
}
}

但这行不通。我应该在包中存储什么才能应用回 PhotoView 以保持缩放级别？

Answer 1

好吧，经过大约 10 个小时的尝试，我已经弄明白了。

为了保存缩放级别，我需要在 Bundle 中保存两个东西，Scale(缩放级别)和 DisplayRect(RectF 类型)。

缩放级别 - 介于 MinScale 和 MaxScale 之间的数字，在我的实例中介于 1 和 16 之间

RectF 包含四个值，出于某种原因，它们是当前 View 的左上角相对于当前屏幕方向的坐标。尽管它包含左上角的坐标，但我不想围绕它旋转，我想围绕中心旋转，所以我需要找到矩形的中心，然后将该值除以“ScreenBase”，这是一个标准化值并使其能够转换为差异平面的值。这是我保存它的方式:

@Override
    protected void onSaveInstanceState( final Bundle outState )
    {
        super.onSaveInstanceState( outState );

        Matrix theMatrix = mPhotoView.getDisplayMatrix();
        float[] theFloat = new float[9];
        theMatrix.getValues( theFloat );
        RectF theRect = mPhotoView.getDisplayRect();


        if (theRect != null)
        {
            if( theRect.left > ( mViewWidth / 2 ) || ( theRect.left >= 0 ) )
            {
                theRect.left = 0;
            }
            else
            {
                theRect.left = ( theRect.left - ( mViewWidth / 2 ) ) / mScreenBase;
            }

            if( theRect.top > ( mViewHeight / 2 ) || ( theRect.top >= 0 ) )
            {
                theRect.top = 0;
            }
            else
            {
                theRect.top = ( theRect.top - ( mViewHeight / 2 ) ) / mScreenBase;

            }
            outState.putParcelable( "RectF", theRect );

            outState.putFloat( "ZoomLevel", mPhotoView.getScale() );
        }
    }

然后当我们在另一边拿起它时，我们必须对数字进行大量操作以使新屏幕空间的左上角以同一位置为中心(如果出现边界问题则对其进行操作) )，这是我的做法:

@Override
    protected void onCreate( final Bundle aSavedInstanceState )
    {
        super.onCreate( aSavedInstanceState );

        mPhotoView = new PhotoView( this );
        mPhotoView.setMaximumScale( 16 );
        setContentView( mPhotoView );
        mPhotoView.setImageResource( R.drawable.vm_app_icon );

        mPhotoView.getViewTreeObserver().addOnPreDrawListener( new ViewTreeObserver.OnPreDrawListener()
        {
            public boolean onPreDraw()
            {
                mPhotoView.getViewTreeObserver().removeOnPreDrawListener( this );
                mViewHeight = mPhotoView.getMeasuredHeight();
                mViewWidth = mPhotoView.getMeasuredWidth();
                Matrix theMatrix = mPhotoView.getDisplayMatrix();
                theMatrix.getValues( mBaseMatrixValues );
                mScreenBase = mBaseMatrixValues[ 0 ];
                int theWidth = mPhotoView.getWidth();
                Log.e(TAG, theWidth + "");

                if( aSavedInstanceState != null )
                {
                    float[] theFloats = new float[ 9 ];
                    float theZoom = aSavedInstanceState.getFloat( "ZoomLevel" );
                    RectF theRect = aSavedInstanceState.getParcelable( "RectF" );
                    theFloats[ 0 ] = theZoom;
                    theFloats[ 4 ] = theZoom;
                    theFloats[ 2 ] = ( theRect.left * mScreenBase ) - ( theZoom * mBaseMatrixValues[ 2 ] ) + ( mViewWidth / 2 ); //Left
                    theFloats[ 5 ] = ( theRect.top * mScreenBase ) - ( theZoom * mBaseMatrixValues[ 5 ] ) + ( mViewHeight / 2 ); //Top
                    theFloats[ 8 ] = (float) 1.0;

                    theFloats = CheckBoundaries( theZoom, theFloats, theRect );

                    theMatrix.setValues( theFloats );
                    mPhotoView.setDisplayMatrix( theMatrix ); //Sets the mSuppMatrix in the PhotoViewAttacher

                    Matrix theImageViewMatrix = mPhotoView.getDisplayMatrix(); //Gets the new mDrawMatrix
                    mPhotoView.setImageMatrix( theImageViewMatrix ); //And applies it to the PhotoView (catches out of boundaries problems)
                }
                return true;
            }
        } );
    }

        private float[] CheckBoundaries(final float aZoom, float[] aFloats, final RectF aRect )
        {
            if( aZoom == 1.0 ) //If the zoom is all the way out
            {
                aFloats[ 2 ] = 0;
                aFloats[ 5 ] = 0;
                return aFloats;
            }

            theMaxLeftValue = ( ( mViewHeight * aZoom ) - mViewWidth + ( aZoom * mBaseMatrixValues[ 2 ] ) );
            theMaxTopValue = ( ( mViewWidth * aZoom ) - mViewHeight + ( aZoom * mBaseMatrixValues[ 5 ] ) );
            if( Math.abs( aFloats[ 2 ] ) > ( theMaxLeftValue ) )
            {
                aFloats[ 2 ] = -Math.abs( theMaxLeftValue ) + 10;
            }
            else if( Math.abs( aFloats[ 2 ] ) < ( aZoom * mBaseMatrixValues[ 2 ] ) )
            {
                aFloats[ 2 ] = -( aZoom * mBaseMatrixValues[ 2 ] );
            }

            if( Math.abs( aFloats[ 5 ] ) > ( theMaxTopValue ) )
            {
                aFloats[ 5 ] = -Math.abs( theMaxTopValue ) + 10;
            }
            else if( Math.abs( aFloats[ 5 ] ) < ( aZoom * mBaseMatrixValues[ 5 ] ) )
            {
                aFloats[ 5 ] = -( aZoom * mBaseMatrixValues[ 5 ] );
            }

            if( aFloats[ 2 ] > 0 )
                aFloats[ 2 ] = -( mViewWidth / 2 );
            else if( aFloats[ 5 ] > 0 )
                aFloats[ 5 ] = -( mViewHeight / 2 );

            return aFloats;
        }