ProgressDialog使用AsyncTask的生产构造未定义错误 [英] ProgressDialog using AsyncTask producing constructor undefined error

问题描述

public class async extends AsyncTask<String, Integer, String>{
ProgressDialog prog;
@Override
protected void onPreExecute() {

    super.onPreExecute();
    prog=new ProgressDialog(async.this);//This is chowing error 
    prog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    prog.setMax(100);
    prog.show();

}

    @Override
    protected String doInBackground(String... params) {
        for (int i = 0; i < 10; i++) {
        publishProgress(5);
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        return null;
    }

@Override
protected void onPostExecute(String result) {

    super.onPostExecute(result);
    prog.dismiss();
}
@Override
protected void onProgressUpdate(Integer... values) {
    prog.setProgress(values[0]);
    super.onProgressUpdate(values);
}
}

以上code为产生错误：

The above code is producing the error:

构造ProgressDialog（AndroidasynctaskActivity.async）是   未定义

the constructor ProgressDialog(AndroidasynctaskActivity.async) is undefined

为什么会这样呢？任何人都可以请帮我解决这个？

Why is this so? Can anyone please help me troubleshoot this?

推荐答案

如前所述，发生这种情况的原因是因为 ProgressDialog 构造你使用需求上下文对象。这里是你如何能做到这一点的一个例子。

As already mentioned, the reason this is happening is because the ProgressDialog constructor you're using needs a Context object. Here's one example of how you can do this.

修改你的异步类，并添加一个接受上下文对象一个参数的构造函数。然后修改在preExecute 的方法来使用说上下文。例如：

Modify your async class and add a single-argument constructor that accepts a Context object. Then modify the onPreExecute method to use said Context. For example:

public class async extends AsyncTask<String, Integer, String>{

  private Context context;
  ProgressDialog prog;

  public async(Context context) {
    this.context = context;
  }


  @Override
  protected void onPreExecute() {
    super.onPreExecute();
    prog=new ProgressDialog(context); 
    prog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    prog.setMax(100);
    prog.show();
  }

  // ...
}

然后实例化并运行此的AsyncTask ：

async mTask = new async(context);
mTask.execute(params);

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