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我知道我必须调用onpause()或ondestroy()停止媒体播放器的方法我必须初始化媒体播放器，但在我的情况下，我调用 html 并使用 android 和 html 之间的接口作为 html 上的调用 android 方法。我尝试从接口中获取实例：

WebAppInterface wb= new WebAppInterface(mContext);

在界面上我初始化了媒体播放器：

public  MediaPlayer mp = MediaPlayer.create(mContext,R.raw.sound);

在主要活动中，我尝试在 oncreate()方法中初始化媒体播放器：

    mediaplayer=wb.mp;

主要活动：

public class Ramadan extends Activity {

private MediaPlayer mediaplayer;

Context mContext;

WebAppInterface wb= new WebAppInterface(mContext);

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity);


    //Call HTML Files
    WebView myWebView = (WebView) findViewById(R.id.web_engine);

    WebSettings webSettings = myWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    myWebView.loadUrl("file:///android_asset/index.html");

    // Intiate interface

    myWebView.addJavascriptInterface(new WebAppInterface(this), "Android");
    mediaplayer=wb.mp;


}
@Override
 protected void onPause()
 {
     super.onPause();
     if(mediaplayer.isPlaying())
     mediaplayer.pause(); //stop the sound
 }

 @Override
 protected void onResume() 
 {
     super.onResume();
     if(WebAppInterface.checked)
     {
         mediaplayer.start();
     }
 }
 @Override
 protected void onDestroy() 
 {
     super.onDestroy();
     if(WebAppInterface.checked)
     {
         mediaplayer.stop();
     }
 }

界面：

Context mContext;
public  MediaPlayer mp = MediaPlayer.create(mContext,R.raw.sound);
 public static boolean checked = false;
/** Instantiate the interface and set the context */
WebAppInterface(Context c) {
    mContext = c;
}


/** Show a toast from the web page */
@JavascriptInterface
public void playsound(String value  ) {
    if (value.equals("on")) {
        checked = true;

        mp.setLooping(true);
        mp.start();
    }
    else 
    {  
        checked = false;
        mp.stop();
    }
}
}

日志猫：

07-01 10:56:20.421: E/AndroidRuntime(636): java.lang.RuntimeException: 
Unable to instantiate activity ComponentInfo{com.ramadan/com.ramadan.Ramadan}:     java.lang.NullPointerException
4

1 回答 1

0

调用 onResume 时，似乎您的媒体播放器尚未初始化。更多关于MediaPlayer 状态图

[编辑-1

并尝试mp在构造函数中进行初始化，即：

public  MediaPlayer mp = null;
public static boolean checked = false;
/** Instantiate the interface and set the context */
WebAppInterface(Context c) {
    mContext = c;
    //Initialize mp here.
    mp = MediaPlayer.create(mContext,R.raw.sound);
}

编辑-1]

[编辑-2

初始化WebAppInterface一次并将该引用传递给addJavascriptInterface(). IE ：

WebAppInterface wb=null;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity);


    //Call HTML Files
    WebView myWebView = (WebView) findViewById(R.id.web_engine);

    WebSettings webSettings = myWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    myWebView.loadUrl("file:///android_asset/index.html");

    //Initialise WebAppInterface and pass this ref..
    wb=new WebAppInterface(this);
    myWebView.addJavascriptInterface(wb, "Android");
    mediaplayer=wb.mp;
}

编辑-2]

于 2013-07-01T09:18:37.190 回答