Question

Actually I programming a app that use image rotation. But when I rotate image, it doesn’t show anything.

This is my code:

XML file:

<?xml version="1.0" encoding="utf-8" ?>

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/rotate_test_layout"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <ImageView
        android:id="@+id/android"
        android:src="@drawable/android"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_gravity="center"
        android:scaleType="matrix"
        android:adjustViewBounds="true"
        android:contentDescription="@string/android_description" >
    </ImageView>

</LinearLayout>

Activity file:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.rotate_test_layout);
    ImageView imageView = (ImageView)findViewById(R.id.android);
    imageView.setScaleType(ScaleType.MATRIX);
    Matrix matrix = new Matrix();
    matrix.postRotate(90);
    imageView.setImageMatrix(matrix);
}

Answer 1

You are making a mistake here:

imageView.setImageMatrix(matrix);

Instead of doing that you have to apply that matrix to the existing Bitmap to get a new bitmap which you can then assign to the ImageView.

Drawable drawable = getResources().getDrawables(R.drawable.android);
Bitmap existingBitmap = ((BitmapDrawable) drawable).getBitmap();
Bitmap rotated = Bitmap.createBitmap(existingBitmap, 0, 0, existingBitmap.getWidth(), existingBitmap.getHeight(), matrix, true);
imageView.setImageBitmap(rotated);