Example ProgressDialog with a second thread

Android 程序開發一定會設計網絡數據下載，不免出現等待時間，爲了緩和用戶的等待時間的“煩躁”，一般會使用進度對話框提升用戶正在進行數據下載，請稍候云云~

下面讓我們看一下android sdk的事例代碼是怎麼指導我們完成這樣的工作的。

1、佈局文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical" android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <TextView android:layout_width="fill_parent"
    android:layout_height="wrap_content" android:text="@string/hello" />
  <Button android:id="@+id/progressBtn" android:layout_width="wrap_content"
    android:layout_height="wrap_content" android:text="HelloProgressBar" />
</LinearLayout>

2、Java代碼：

package com.penguin7.hello;

import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.widget.Button;

public class HelloAndroid extends Activity {
  private static final int PROGRESS_DIALOG = 0;
  private ProgressDialog mProgressDlg = null;
  private ProgressThread mProgressThd = null;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    // Setup the button that starts the progress dialog
    Button btnProgress = (Button) findViewById(R.id.progressBtn);
    btnProgress.setOnClickListener(new View.OnClickListener() {
      public void onClick(View v) {
        showDialog(PROGRESS_DIALOG);
      }
    });
  }

  @Override
  protected Dialog onCreateDialog(int id) {

    switch (id) {
    case PROGRESS_DIALOG:
      mProgressDlg = new ProgressDialog(this);
      mProgressDlg.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
      mProgressDlg.setTitle("Loading...");
      mProgressDlg.setMessage("Please wait for a while...");
                        mProgressThd = new ProgressThread(handler);
                        mProgressThd.start();
      return mProgressDlg;
    default:
      return null;
    }
  }

  // Define the Handler that receives messages from the thread and update the
  // progress
  private final Handler handler = new Handler() {
    public void handleMessage(Message msg) {
      int total = msg.getData().getInt("total");
      mProgressDlg.setProgress(total);
      if (total >= 100) {
        dismissDialog(PROGRESS_DIALOG);
        mProgressThd.setState(ProgressThread.STATE_DONE);
      }
    }
  };

  /** Nested class that performs progress calculations (counting) */
  private class ProgressThread extends Thread {
    Handler mHandler = null;
    private final static int STATE_DONE = 0;
    private final static int STATE_RUNNING = 1;
    private int mState = 0;

    ProgressThread(Handler h) {
      this.mHandler = h;
    }

    public void run() {
      setState(STATE_RUNNING);
      int total = 0;
      while (STATE_RUNNING == mState) {
        try {
          Thread.sleep(100);
        } catch (InterruptedException e) {
          Log.e("ERROR", "Thread Interrupted");
        }
        Message msg = mHandler.obtainMessage();
        Bundle b = new Bundle();
        b.putInt("total", total);
        msg.setData(b);
        mHandler.sendMessage(msg);
        total++;
      }
    }

    /**
     * sets the current state for the thread, used to stop the thread
     */
    public void setState(int state) {
      mState = state;
    }
  }

}

3、看看效果：