Android转场动画——共享元素

<!--第一个Activity的xml布局，需要共享的元素，加上transitionName属性。至于名字，你随便定义，要保持相同-->
<?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"
    android:gravity="bottom"
    tools:context="com.haichenyi.activitytransitionanimation.MainActivity">

    <ImageView
        android:id="@+id/img"
        android:layout_width="300dp"
        android:layout_height="200dp"
        android:transitionName="wang"
        android:src="@mipmap/bg"/>

    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="跳转"/>
</LinearLayout>

<!--第二个activity的xml布局-->
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/img"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:src="@mipmap/bg"
        android:transitionName="wang"/>
    <Button
        android:id="@+id/btn"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="back"/>
</android.support.constraint.ConstraintLayout>

/**
 * Author: 海晨忆.
 * Date: 2018/3/29
 * Desc:
 */
public class MainActivity extends AppCompatActivity {

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

    findViewById(R.id.btn).setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
      //共享元素转场动画，只支持android 5.0，所以加一个判断
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
          startActivity(new Intent(MainActivity.this, Step1Activity.class),
              ActivityOptions.makeSceneTransitionAnimation(MainActivity.this,
                  findViewById(R.id.img), "wang").toBundle());
        } else {
          startActivity(new Intent(MainActivity.this, Step1Activity.class));
        }
      }
    });
  }
}

ActivityOptions.makeSceneTransitionAnimation(Activity activity,
            View sharedElement, String sharedElementName)