1

好的,你们都是超级 java/android 大师。我知道你会看到这个并大笑,但我真的需要帮助。我是一个超级新手,已经阅读了所有谷歌开发文档(以及更多),但无法掌握这个概念。可以通过查看工作代码而不是推荐我已经阅读但显然不理解的东西来学习更多,所以如果有人可以帮助我,那就太好了。

主要活动

 import java.util.Timer;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import android.app.Activity;
 import android.app.ProgressDialog;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.preference.PreferenceManager;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.webkit.WebView;

 public class Quotes extends Activity implements OnClickListener {

 ProgressDialog dialog;
private WebView webview;
private Timer timer;

 @Override
 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    WebView adsview = (WebView) findViewById(R.id.ads);
    adsview.getSettings().setJavaScriptEnabled(true);
    adsview.loadUrl("http://www.dgdevelco.com/quotes/androidad.html");

    SharedPreferences SP = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

    String q = SP.getString("appViewType","http://www.dgdevelco.com/quotes/quotesandroidtxt.html");
    String c = SP.getString("appRefreshRate","20");

    webview = (WebView) findViewById(R.id.scroll);
    webview.getSettings().setJavaScriptEnabled(true);
    webview.setWebViewClient(new QuotesWebView(this));
    webview.loadUrl(q);



    ScheduledExecutorService timer = Executors.newSingleThreadScheduledExecutor();
    timer.scheduleAtFixedRate(new Runnable() {

        @Override
        public void run() {
            webview.reload();

            }

        }, 10, Long.parseLong(c),TimeUnit.SECONDS);




    findViewById(R.id.refresh).setOnClickListener(this);


 }

 @Override
 public void onPause(){
   timer.cancel(); 
   super.onPause();
 }

 @Override
 public void onResume(){
  webview.reload();
      super.onResume();
 }


 public void onClick(View v){
    switch(v.getId()){
    case R.id.refresh:
         webview.reload();
         break;
         }
    }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);

    MenuItem about = menu.getItem(0);
    about.setIntent(new Intent(this, About.class));

    MenuItem preferences = menu.getItem(1);
    preferences.setIntent(new Intent(this, Preferences.class));

    return true;

 }



 }   

目录日志

 07-05 17:28:51.001: DEBUG/AndroidRuntime(11446): Shutting down VM
 07-05 17:28:51.001: WARN/dalvikvm(11446): threadid=1: thread exiting with uncaught exception (group=0x40018560)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446): FATAL EXCEPTION: main
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446): java.lang.RuntimeException: Unable to pause activity {com.dge.quotes/com.dge.quotes.Quotes}: java.lang.NullPointerException
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2477)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2424)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread.handlePauseActivity(ActivityThread.java:2404)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread.access$1700(ActivityThread.java:124)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:979)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.os.Handler.dispatchMessage(Handler.java:99)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.os.Looper.loop(Looper.java:123)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread.main(ActivityThread.java:3806)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at java.lang.reflect.Method.invokeNative(Native Method)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at java.lang.reflect.Method.invoke(Method.java:507)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at dalvik.system.NativeStart.main(Native Method)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446): Caused by: java.lang.NullPointerException
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at com.dge.quotes.Quotes.onPause(Quotes.java:72)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.Activity.performPause(Activity.java:3901)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.Instrumentation.callActivityOnPause(Instrumentation.java:1191)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     at android.app.ActivityThread.performPauseActivity(ActivityThread.java:2459)
 07-05 17:28:51.017: ERROR/AndroidRuntime(11446):     ... 12 more
 07-05 17:28:51.509: WARN/ActivityManager(1319): Activity pause timeout for HistoryRecord{40ba7e20 com.dge.quotes/.Quotes}

任何和所有的帮助将不胜感激。

在这一点上,我觉得自己像一个完全疯狂的女人,她真的需要完成这个项目,这样我的生活才能继续前进。如果有人(任何人)对此有答案,我会非常感激。

4

3 回答 3

1

您在活动中有一个名为 timer 的私有计时器,但是似乎尚未初始化,因为您的活动中有另一个名为 timer 的计时器。您在 webview 下定义的私有 Timer 计时器为 null,因此在调用 onPause 时您会得到 nullpointexception。

从 onCreate() 中删除类,您可能需要将 Timer 定义为 singlethreadscheduledexecutor。

timer = Executors.newSingleThreadScheduledExecutor();
timer.scheduleAtFixedRate(new Runnable() {

您带有建议答案的代码:

import java.util.Timer;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 import android.app.Activity;
 import android.app.ProgressDialog;
 import android.content.Intent;
 import android.content.SharedPreferences;
 import android.os.Bundle;
 import android.preference.PreferenceManager;
 import android.view.Menu;
 import android.view.MenuInflater;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.webkit.WebView;

 public class Quotes extends Activity implements OnClickListener {

 ProgressDialog dialog;
private WebView webview;
private Timer timer;

 @Override
 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    WebView adsview = (WebView) findViewById(R.id.ads);
    adsview.getSettings().setJavaScriptEnabled(true);
    adsview.loadUrl("http://www.dgdevelco.com/quotes/androidad.html");

    SharedPreferences SP = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

    String q = SP.getString("appViewType","http://www.dgdevelco.com/quotes/quotesandroidtxt.html");
    String c = SP.getString("appRefreshRate","20");

    webview = (WebView) findViewById(R.id.scroll);
    webview.getSettings().setJavaScriptEnabled(true);
    webview.setWebViewClient(new QuotesWebView(this));
    webview.loadUrl(q);



    timer = Executors.newSingleThreadScheduledExecutor();
    timer.scheduleAtFixedRate(new Runnable() {

        @Override
        public void run() {
            webview.reload();

            }

        }, 10, Long.parseLong(c),TimeUnit.SECONDS);




    findViewById(R.id.refresh).setOnClickListener(this);


 }

 @Override
 public void onPause(){
   timer.cancel(); 
   super.onPause();
 }

 @Override
 public void onResume(){
  webview.reload();
      super.onResume();
 }


 public void onClick(View v){
    switch(v.getId()){
    case R.id.refresh:
         webview.reload();
         break;
         }
    }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.menu, menu);

    MenuItem about = menu.getItem(0);
    about.setIntent(new Intent(this, About.class));

    MenuItem preferences = menu.getItem(1);
    preferences.setIntent(new Intent(this, Preferences.class));

    return true;

 }



 }   
于 2011-07-07T23:26:51.140 回答
0

您可以尝试在您的活动中拦截 onBackPressed,然后执行 timer.cancel()。就像是

@Override
public void onBackPressed() {
    timer.cancel();
}
于 2011-07-06T00:07:06.250 回答
0

onStop() 是放置 timer.cancel() 的更可靠的位置(或者如果您想涵盖几乎所有情况,例如此处末尾所述的情况,则可以同时放置这两个位置)。

onPause() 并非在所有情况下都被调用,它在 onResume() 合理可能发生时使用,例如当您进行另一个活动然后返回时。注意生命周期大纲中的缩进。按下后退按钮时可能不会调用它。

编辑 1:这是一个预编辑答案,因此可能无法涵盖强制关闭问题。

编辑2:

@Override
public void onStop(){
    super.onStop();
    try {
        timer.cancel();
    } catch (Exception ex) {
        Log.e("MY APP ERROR", ex.getMessage());
    }
}

在这些生命周期方法中,我总是把对 super 的调用放在首位。我不确定这是否有所作为。您可能还想设置 try/catch 语句,尤其是当您选择在 onStop() 和 onPause() 中都包含 timer.cancel() 时。

编辑3:关于准备承认失败。我对 ScheduledExecutorService 的怪癖不是很熟悉,既然你已经说过你愿意重写,这就是我如何在我的应用程序中完成相同的事情。Handler 是一个特定于 Android 的实现,所以也许这就是为什么我没有遇到你遇到的同样的麻烦。

Handler timer;
Runnable runner;

@Override
onCreate(...) {
    ...

    //EDIT 4: (reading time from preferences)
    SharedPreferences SP = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

    final int c = Integer.parseInt(SP.getString("appRefreshRate","20"));

    ...

    runner = new Runnable() {
        @Override
        public void run() {
            timer.postDelayed(runner, c * 1000);
            webview.reload();
        }
    };
    timer = new Handler();
    timer.postDelayed(runner, c * 1000);

    ...
}

@Override
public void onPause(){
    super.onPause();
    try {
        timer.removeCallbacks(runner);
    } catch (Exception ex) {
        Log.e("MY APP ERROR", ex.getMessage());
    }
}

@Override
public void onStop(){
    super.onStop();
    try {
        timer.removeCallbacks(runner);
    } catch (Exception ex) {
        Log.e("MY APP ERROR", ex.getMessage());
    }
}
于 2011-07-06T00:29:52.073 回答