如何使ImageView生效

Question

期望：

我想在public class MainActivity extends AppCompatActivity { SwipeRefreshLayout swipeRefreshLayout; TextView DateView; TextView tvtitle; SimpleDateFormat sdf; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); swipeRefreshLayout = findViewById(R.id.swipe_test); tvtitle = findViewById(R.id.tv_title); DateView = findViewById(R.id.tv_date); sdf = new SimpleDateFormat("dd.MM.yyyy - HH:mm:ss z"); swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() { @Override public void onRefresh() { getDate(); new Handler().postDelayed(new Runnable() { @Override public void run() { swipeRefreshLayout.setRefreshing(false); } },1500); } }); } public void getDate(){ String currentDateandTime = sdf.format(new Date()); DateView.setText(currentDateandTime); } } 的顶部（仅在顶部）像黑色阴影一样产生效果。我尝试为ImageView的背景创建形状，如下所示：

ImageView

但是它不起作用。有解决方案吗？

Answer 1

活动或片段的布局

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

<ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@drawable/ic_launcher_background"
        android:adjustViewBounds="true" />

<View
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/shadoweffects" />
 </FrameLayout>

drawable shadoweffects.xml

<shape xmlns:android="http://schemas.android.com/apk/res/android"
   android:shape="rectangle">

<gradient
        android:angle="90"
        android:endColor="#aa000000"    
        android:startColor="#00ffffff"
        android:centerColor="#00ffffff" />
</shape>

根据要求更改颜色