应用于Bitmap的Android Matrix postRotate和postTranslate

Question

以下是我编写的代码片段，试图理解Matrix（postRotate和postTranslate更为准确）。

活动：

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private ImageView mImageView2;

    @Override
    public void onClick(final View v) {
        switch (v.getId()) {
            case R.id.btn:

                Matrix matrix = new Matrix();
                matrix.postRotate(90);
                matrix.postTranslate(200, 0);

                Bitmap bitmap =
                        BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher, null);

                Bitmap bitmap2 = Bitmap.createBitmap(
                        bitmap,
                        0,
                        0,
                        bitmap.getWidth(),
                        bitmap.getHeight(),
                        matrix,
                        true
                );

                mImageView2.setImageBitmap(bitmap2);
                break;
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        findViewById(R.id.btn).setOnClickListener(this);
        mImageView2 = (ImageView) findViewById(R.id.image2);
    }
}

XML布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="sample2.com.sample_app.MainActivity">

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

    <ImageView
        android:id="@+id/image2"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#ccc"
        android:scaleType="matrix"
        tools:src="@mipmap/ic_launcher" />

</LinearLayout>

问题是位图已旋转但未移动到任何位置：

我做错了什么？