<!-- 顯示系統(tǒng)窗口權限 -->
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>
<!-- 在 屏幕最頂部顯示-->
<uses-permission android:name="android.permission.SYSTEM_OVERLAY_WINDOW" />

if (Build.VERSION.SDK_INT >= 23) {
            if (!Settings.canDrawOverlays(MainActivity.this)) {
                Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                        Uri.parse("package:" + getPackageName()));
                startActivityForResult(intent, 10);
            }
        }
        
 @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == 10) {
            if (Build.VERSION.SDK_INT >= 23) {
                if (!Settings.canDrawOverlays(this)) {
                    // SYSTEM_ALERT_WINDOW permission not granted...
                    Toast.makeText(MainActivity.this, "not granted", Toast.LENGTH_SHORT);
                }
            }
        }
        super.onActivityResult(requestCode, resultCode, data);
    }

public class DifferentDisplay extends Presentation {
    public DifferentDisplay(Context outerContext, Display display) {
        super(outerContext, display);
    }

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

    public void setText(String text) {
        TextView textView = findViewById(R.id.tv_test);
        textView.setText(text);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:background="@color/purple_200"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/tv_test"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="異顯"
        android:textSize="50sp" />

</RelativeLayout>

public class MainActivity extends AppCompatActivity {
    final String TAG = "MainActivity";
    DifferentDisplay mPresentation;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 雙屏顯示
        DisplayManager mDisplayManager; //屏幕管理類
        Display[] displays;// 屏幕數(shù)組
        mDisplayManager = (DisplayManager) MainActivity.this.getSystemService(Context.DISPLAY_SERVICE);
        displays = mDisplayManager.getDisplays(); // 得到顯示器數(shù)組
        if (displays.length == 0) {
            Log.d(TAG, "無顯示屏");
            return;
        }
        mPresentation = new DifferentDisplay(getApplicationContext(), displays[1]);//displays[1]是副屏
       // 8.0 需要替換為 TYPE_APPLICATION_OVERLAY mPresentation.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);
        mPresentation.show();
    }

    int index = 1;

    public void Test(View view) {
        if (mPresentation != null)
            mPresentation.setText(++index + "點擊");
    }
}

mPresentation.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);