Question

我正在开发一个Android应用程序，其中有活动列表。在某个时间启动任何活动。所以想要包括progess栏直到下一个活动启动。

我在进度条上经历了很多问题但是没有得到确切的解决方案。所以，任何人都可以建议我在我的应用程序中集成进度条的最佳方法。

我正在分享我的代码，而logCat无法正常工作。

  package com.example.progress;

  import android.app.Activity;
  import android.app.ProgressDialog;
  import android.content.Intent;
  import android.os.Bundle;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.view.View;
  import android.view.View.OnClickListener;
  import android.widget.Button;

  public class MainActivity extends Activity {

  private ProgressDialog progress;
  Button Button;

    @Override
    protected void onCreate(Bundle savedInstanceState) 
    {
     progress = new ProgressDialog(MainActivity.this);
     Button=(Button)findViewById(R.id.button1);

      Button.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
             switch (v.getId()) {
                case R.id.button1:
                     progress.setMessage("Please Wait Loading...");
               progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);
               progress.setIndeterminate(true);
            progress.show();
             new Thread() 
             {

                 public void run() 
                 {

                     Intent i = new Intent(MainActivity.this,Second.class);
                     startActivity(i);
                     progress.dismiss();
                 }

             }.start();


                    break;
        }

        }
    });
    }
}

  LOgCat Error :::
  -----------   



       01-27 17:23:19.094: D/AndroidRuntime(13666): Shutting down VM
       01-27 17:23:19.095: E/AndroidRuntime(13666): FATAL EXCEPTION: main
       01-27 17:23:19.095: E/AndroidRuntime(13666): Process: com.example.progress, PID:  13666
       01-27 17:23:19.095: E/AndroidRuntime(13666): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.progress/com.example.progress.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        01-27 17:23:19.095: E/AndroidRuntime(13666):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2339)
        01-27 17:23:19.095: E/AndroidRuntime(13666):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at android.app.ActivityThread.access$800(ActivityThread.java:155)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at android.os.Handler.dispatchMessage(Handler.java:102)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at android.os.Looper.loop(Looper.java:135)
     01-27 17:23:19.095: E/AndroidRuntime(13666):   at android.app.ActivityThread.main(ActivityThread.java:5343)
     01-27 17:23:19.095: E/AndroidRuntime(13666):   at java.lang.reflect.Method.invoke(Native Method)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at java.lang.reflect.Method.invoke(Method.java:372)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:702)
      01-27 17:23:19.095: E/AndroidRuntime(13666): Caused by:   java.lang.NullPointerException: Attempt to invoke virtual method 'void  android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
       01-27 17:23:19.095: E/AndroidRuntime(13666):     at com.example.progress.MainActivity.onCreate(MainActivity.java:22)
       01-27 17:23:19.095: E/AndroidRuntime(13666):     at android.app.Activity.performCreate(Activity.java:6010)
       01-27 17:23:19.095: E/AndroidRuntime(13666):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1129)
      01-27 17:23:19.095: E/AndroidRuntime(13666):  at      android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292)
       01-27 17:23:19.095: E/AndroidRuntime(13666):     ... 10 more

Answer 1

假设您的活动显示简单列表视图

 private ProgressBar mProgBar;
mProgBar= (ProgressBar) findViewById(R.id.progressBarMain);
mProgBar.setVisibility(View.VISIBLE); //before doing your desired operation

/*     do your stuff here  populate your listview     */


mProgBar.setVisibility(View.INVISIBLE); //hide the progressbar
//display your list here

Answer 2

当您点击Progressbar转到下一个活动或启动它时，如何启动Button，然后停止/关闭onPause()中的栏？

Answer 3

尝试修改onClick()，如下所示，看progressBar正常工作由于您的progressBar属于当前Activity，因此当您启动另一个Activity时，您无法看到progress bar

Button.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
             switch (v.getId()) {
                case R.id.button1:
                     progress.setMessage("Please Wait Loading...");
               progress.setProgressStyle(ProgressDialog.STYLE_SPINNER);
               progress.setIndeterminate(true);
            progress.show();
             new Thread() 
             {

                 public void run() 
                 {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
                     Intent i = new Intent(MainActivity.this,Second.class);
                     startActivity(i);
                     progress.dismiss();
                 }

             }.start();


                    break;
        }

        }
    });

如何在进入下一个活动之前包含进度条？

3 个答案: