创建“加载"动画轻松 [英] Create "loading" animation easily

问题描述

我有一个 android listView，每个项目都有一个图像.加载图像需要一段时间.如何在每次加载图像时添加加载"动画?

I have an android listView with an image in each item. It takes a while till the image is loaded. How can I add a "loading" animation every time the image is loaded?

我应该使用 .gif 吗?或者创建我自己的动画并在 onPostExecute() 上停止它?

Should I use a .gif? Or create my own animation and stop it on onPostExecute()?

如果我使用picasso"，我该怎么做，因为所有的异步任务对开发者来说都是黑匣子，我无法停止任何动画?

How can I do this if I use "picasso" because there all the async task is black box to the developer and I cannot stop any animation?

推荐答案

使用以下代码:

MainActivity.java

MainActivity.java

@Override
protected 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

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

ListAdapter.java

@Override
public 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;
}

不要忘记为毕加索回调添加导入

Don't forget to add import for Picasso Callback

import com.squareup.picasso.Callback;

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