PHP应用：Android AsyncTack 异步任务实例详解

PHP实例
/* 唯一执行在子线程中的方法
 *  所以不可以进行UI的更新
 * @param params
 * @return
 */
@Override//返回值: Result    参数: Param
protected String doInBackground(TextView... params) {
  text = params[0];
  Random random = new Random();
  for (int i = 0; i < 50; i++) {
    //要进行进度的更新
    publishProgress(i);
    //不能直接调用onProgressUpdate方法,
    //这样会使得onProgressUpdate在子线程中运行
    try {
      Thread.sleep(random.nextInt(10) * 10);
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
  }
  return "已完成";
}

PHP实例
 //执行doInBackground之前调用
  @Override
  protected void onPreExecute() {
    super.onPreExecute();
  }

PHP实例
  @Override//与publishProgress(i)对应
  protected void onProgressUpdate(Integer... values) {
    super.onProgressUpdate(values);
    text.setText(String.valueOf(values[0]));
  }

PHP实例
 //在doInBackground之后执行
  @Override // 参数s为 Result
  protected void onPostExecute(String s) {
    super.onPostExecute(s);
    text.setText(s);
  }

PHP实例
有两种方式, 我已经把区别写在了注释中
/*
 直接execute异步任务, 都是同一线程去执行
*/
text = (TextView) findViewById(R.id.main_text1);
new MyTask().execute(text);
text = (TextView) findViewById(R.id.main_text2);
new MyTask().execute(text);
text = (TextView) findViewById(R.id.main_text3);
new MyTask().execute(text);
text = (TextView) findViewById(R.id.main_text4);
new MyTask().execute(text);

PHP实例
/*
  启动多条线程来执行异步任务
  API11以上可以使用
*/
 ScheduledThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(4);
 text = (TextView) findViewById(R.id.main_text1);
 new MyTask().executeOnExecutor(executor, text);
 text = (TextView) findViewById(R.id.main_text2);
 new MyTask().executeOnExecutor(executor, text);
 text = (TextView) findViewById(R.id.main_text3);
 new MyTask().executeOnExecutor(executor, text);
 text = (TextView) findViewById(R.id.main_text4);
 new MyTask().executeOnExecutor(executor, text);

PHP实例
<ScrollView
  android:layout_width="match_parent"
  android:layout_height="match_parent">
  <LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ImageView
      android:id="@+id/main2_image"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content" />
    <WebView
      android:id="@+id/main2_web"
      android:layout_width="match_parent"
      android:layout_height="match_parent"/>
  </LinearLayout>
</ScrollView>

PHP实例
public class Entry {
  @SerializedName("title")
  private String title;
  @SerializedName("message")
  private String message;
  @SerializedName("img")
  private String image;
  public String getTitle() {
    return title;
  }
  ...//省略其余getter和setter方法
  public void setImage(String image) {
    this.image = image;
  }
}

PHP实例
/**
 * Created by Lulu on 2016/8/31.
 * <p/>
 * 通用下载工具类
 */
public class NetWorkTask<T> extends AsyncTask<NetWorkTask.Callback<T>, Void, Object> {
  private NetWorkTask.Callback<T> callback;
  private Class<T> t;
  private String url;
  public NetWorkTask(String url, Class<T> t) {
    this.url = url;
    this.t = t;
  }
  @Override
  protected Object doInBackground(Callback<T>... params) {
    callback = params[0];
    try {
      HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
      connection.setRequestMethod("GET");
      connection.setDoInput(true);
      int code = connection.getResponseCode();
      if (code == 200) {
        InputStream is = connection.getInputStream();
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buffer = new byte[102400];
        int length;
        while ((length = is.read(buffer)) != -1) {
          bos.write(buffer, 0, length);
        }
        return bos.toString("UTF-8");
      } else {
        return new RuntimeException("服务器异常");
      }
    } catch (Exception e) {
      e.printStackTrace();
      return e;
    }
  }
  @Override
  protected void onPostExecute(Object o) {
    super.onPostExecute(o);
    if(o instanceof String) {
      String str = (String) o;
      Gson gson = new Gson();
      T t = gson.fromJson(str, this.t);
      callback.onSuccess(t);
    }
    if( o instanceof Exception) {
      Exception e = (Exception) o;
      callback.onFailed(e);
    }
  }
  public interface Callback<S> {
    void onSuccess(S t);
    void onFailed(Exception e);
  }
}

PHP实例
/**
 * Created by Lulu on 2016/8/31.
 * 图片网络加载器
 * 下载成功返回Bitmap
 * 否则返回null
 */
public class ImageLoader extends AsyncTask<String, Void, Bitmap>{
  private ImageView image;
  public ImageLoader(ImageView image) {
    this.image = image;
    image.setImageResource(R.mipmap.ic_launcher);
  }
  @Override
  protected void onPreExecute() {
    super.onPreExecute();
  }
  @Override
  protected Bitmap doInBackground(String... params) {
    String url = params[0];
    try {
      HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
      connection.setRequestMethod("GET");
      connection.setDoInput(true);
      int code = connection.getResponseCode();
      if (code == 200) {
        InputStream is = connection.getInputStream();
        return BitmapFactory.decodeStream(is);
      }
    } catch (IOException e) {
      e.printStackTrace();
    }
    return null;
  }
  @Override
  protected void onPostExecute(Bitmap bitmap) {
    super.onPostExecute(bitmap);
    if (bitmap != null) {
      image.setImageBitmap(bitmap);
    } else {
      image.setImageResource(R.mipmap.failed);
    }
  }
}

PHP实例
public class Main2Activity extends AppCompatActivity implements NetWorkTask.Callback<Entry>{
  private WebView web;
  private ImageView image;
  //解决大图在webView中不左右滑动的问题
  private static final String CSS = "<style>img{max-width:100%} </style>";
  private String title;
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    web = (WebView) findViewById(R.id.main2_web);
    image = (ImageView) findViewById(R.id.main2_image);
    new NetWorkTask<>("http://www.tngou.net/api/top/show?id=13122", Entry.class).execute(this);
  }
  @Override
  public void onSuccess(Entry t) {
    web.loadDataWithBaseURL("", t.getMessage(), "text/html; charset=utf-8", "UTF-8", null);
    new ImageLoader(image).execute("http://img.blog.csdn.net/20160829134937003");
  }
  @Override
  public void onFailed(Exception e) {
    web.loadDataWithBaseURL("", "加载失败", "text/html; charset=utf-8", "UTF-8", null);
  }
}