轻松创建“加载”动画

使用以下代码：

MainActivity.java

@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_my);    ArrayList<HashMap<String, String>> itemsList = new ArrayList<HashMap<String, String>>();    ListView listView = (ListView) findViewById(R.id.listView);    for (int i = 0; i < 5; i++) {        // creating new HashMap        HashMap<String, String> map = new HashMap<String, String>();        // adding each child node to HashMap key =&gt; value        map.put("key1", "value1");        map.put("key2", "value2");        // adding HashList to ArrayList        itemsList.add(map);    }    ListAdapter listAdapter = new ListAdapter(this, itemsList);    listView.setAdapter(listAdapter);}

list_row.xml

<?xml version="1.0" encoding="utf-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"><ImageView    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:id="@+id/imageView"    android:layout_alignParentTop="true"    android:layout_alignParentLeft="true"    android:layout_alignParentStart="true"    android:src="@drawable/ic_launcher" /><ProgressBar    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:id="@+id/progressBar"    android:layout_toEndOf="@+id/imageView"    android:layout_alignParentTop="true"    android:layout_alignParentLeft="true"    android:layout_alignParentStart="true" /></RelativeLayout>

ListAdapter.java

@Overridepublic View getView(int position, View convertView, ViewGroup parent) {    View vi = convertView;    if (convertView == null)        vi = inflater.inflate(R.layout.list_row, null);    ImageView imageView = (ImageView) vi.findViewById(R.id.imageView);    final ProgressBar progressBar = (ProgressBar) vi.findViewById(R.id.progressBar);    //This line shows progressBar again for recycled view    progressBar.setVisibility(View.VISIBLE);    Picasso.with(activity.getApplicationContext()).load(imagePath).resize(100, 100) .into(imageView, new Callback() {     @Override     public void onSuccess() {         progressBar.setVisibility(View.GONE);     }     @Override     public void onError() {         //error     } });    return vi;}

别忘了为Picasso Callback添加导入

import com.squareup.picasso.Callback;