Question

我尝试做什么

我有一个ListView，里面有一个OnItemClick，在那里我得到了我存储的URL，用这个URL我设置了一个Intent到另一个Activity（WebView）打开，网页。

问题

当我试图获得意图时，我总是得到一个强制关闭错误，但我不明白为什么。如果你发现错误会很好:(

您在此处找到的两项活动的代码：

代码

test2.java - ＆gt;在这里，我创建了Intent

package de.stepforward;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;


import org.json.JSONArray;
import org.json.JSONObject;

import de.stepforward.web.ShowVideo;



import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;



public class test2 extends ListActivity {


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


    String result = "";
    String line = null;
    final ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();


    //get the Data from URL
    try{
    URL url = new URL("http://gdata.youtube.com/feeds/mobile/users/TheStepForward/uploads?alt=json&format=1"); 

    URLConnection conn = url.openConnection();
    StringBuilder sb = new StringBuilder();
    BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));

    //read d response till d end
    while ((line = rd.readLine()) != null) {
    sb.append(line + "\n");
    }
    result = sb.toString();
    Log.v("log_tag", "Append String " + result);
    } catch (Exception e) {
    Log.e("log_tag", "Error converting result " + e.toString());
    }

    try{
        JSONObject json = new JSONObject(result);
        JSONObject feed = json.getJSONObject("feed");
        JSONArray entrylist = feed.getJSONArray("entry");

        for(int i=0;i<entrylist.length();i++){
            //Get Title
            JSONObject movie = entrylist.getJSONObject(i);
            JSONObject title = movie.getJSONObject("title");
            String txtTitle = title.getString("$t");
            Log.d("Title", txtTitle);

            //Get Description
            JSONObject content = movie.getJSONObject("content");
            String txtContent = content.getString("$t");
            Log.d("Content", txtContent);

            //Get Link
            JSONArray linklist = movie.getJSONArray("link");
            JSONObject link = linklist.getJSONObject(0);
            String txtLink = link.getString("href");
            Log.d("Link", txtLink);


            //Get Thumbnail
            JSONObject medialist = movie.getJSONObject("media$group");
            JSONArray thumblist = medialist.getJSONArray("media$thumbnail");
            JSONObject thumb = thumblist.getJSONObject(2);
            String txtThumb = thumb.getString("url");
            Log.d("Thumb", txtThumb.toString());


            //String Array daraus machen und in Hashmap füllen
            HashMap<String, String> map = new HashMap<String, String>();
            map.put("Thumb", txtThumb);
            map.put("Title", txtTitle);
            map.put("Content", txtContent);
            map.put("Link", txtLink);
            mylist.add(map);

        }
        //ListView füllen
        ListAdapter adapter = new SimpleAdapter(this, mylist , R.layout.lit, 
                new String[] { "Thumb","Title","Content","Link"}, 
                new int[] { R.id.img_video,R.id.txt_title,R.id.txt_subtitle});      
        setListAdapter(adapter);


        //OnClickLister um Youtube-Video zu öffnen
        final ListView lv = getListView();
            lv.setOnItemClickListener(new OnItemClickListener(){
                public void onItemClick(AdapterView<?> parent, View v, int position, long id) {

                    //Video-Link auslesen
                    Map<String, String> map = mylist.get(position);
                    String link = map.get("Link");
                    Log.d("Link", link);

                    final Intent Showvideo = new Intent(test2.this, ShowVideo.class);
                    Showvideo.putExtra("VideoLink", link);

                    final Intent i = new Intent(test2.this, ShowVideo.class);
                    startActivity(i);

                }
            });



    }catch (Exception e) {
        Log.e("log_tag", "Error converting result " + e.toString());
        }
}
}

Showvideo.java - ＆gt;在这里，我收到了意图

package de.stepforward.web;

import de.stepforward.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.KeyEvent;
import android.webkit.WebView;
import android.webkit.WebViewClient;


public class ShowVideo extends Activity {

    WebView mWebView;


    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK) && mWebView.canGoBack()) {
            mWebView.goBack();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }

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


    //Video-Link abfangen
    Bundle extras = getIntent().getExtras();
    String VideoLink = extras.getString("ShowVideo");


    mWebView = (WebView) findViewById(R.id.webview);
    mWebView.getSettings().setJavaScriptEnabled(true);
    mWebView.loadUrl(VideoLink);



    }




}

提前感谢您的帮助！

最好的问候

狩猎

注意：抱歉忘了错误日志。你在这里：

错误-登录

11-29 08:57:57.258: W/dalvikvm(10944): threadid=1: thread exiting with uncaught exception (group=0x4001d5a0)
11-29 08:57:57.258: E/AndroidRuntime(10944): FATAL EXCEPTION: main
11-29 08:57:57.258: E/AndroidRuntime(10944): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.stepforward/de.stepforward.web.ShowVideo}: java.lang.NullPointerException
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1816)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1837)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.ActivityThread.access$1500(ActivityThread.java:132)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1033)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.os.Handler.dispatchMessage(Handler.java:99)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.os.Looper.loop(Looper.java:143)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.ActivityThread.main(ActivityThread.java:4196)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at java.lang.reflect.Method.invokeNative(Native Method)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at java.lang.reflect.Method.invoke(Method.java:507)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at dalvik.system.NativeStart.main(Native Method)
11-29 08:57:57.258: E/AndroidRuntime(10944): Caused by: java.lang.NullPointerException
11-29 08:57:57.258: E/AndroidRuntime(10944):    at de.stepforward.web.ShowVideo.onCreate(ShowVideo.java:33)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1093)
11-29 08:57:57.258: E/AndroidRuntime(10944):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1780)
11-29 08:57:57.258: E/AndroidRuntime(10944):    ... 11 more

Answer 1

在你写这行的时间

Showvideo.putExtra("VideoLink", link);

在你写的时候

Bundle extras = getIntent().getExtras();
String VideoLink = extras.getString("ShowVideo");

因为您必须使用相同的键来获取和设置时间，因此您将VideoLink设置为关键并使用未设置的ShowVideo获取时间

试试这种方式

Bundle extras = getIntent().getExtras();
String VideoLink = extras.getString("VideoLink");

Answer 2

这是什么？为什么你写了2个意图并将额外传递给另一个意图。

  final Intent Showvideo = new Intent(test2.this, ShowVideo.class);
                        Showvideo.putExtra("VideoLink", link);

                        final Intent i = new Intent(test2.this, ShowVideo.class);
                        startActivity(i);

在这个ShowVideo活动中，您将获得额外内容，因为关键是“ShowVideo”。但你传递的是“VideoLink”。

 String VideoLink = extras.getString("ShowVideo");

这就是为什么你得到nullpointer来获取额外的第33行。

Answer 3

首先，请在开头写一个带有小写字母和类名的变量名，并带一个大字母。每个名字都有Camel-case;

所以对于你的问题，我认为这两个答案应该解决它。只是将它放在一个地方，你的onItemClick方法应该是这样的。

public void onItemClick(AdapterView<?> parent, View v, int position, long id) {

                //Video-Link auslesen
                Map<String, String> map = myList.get(position);
                String link = map.get("Link");
                Log.d("Link", link);

                Intent i = new Intent(test2.this, ShowVideo.class);
                i.putExtra("VideoLink", link);
                startActivity(i);

            }

首先，您不必创建2个意图。您只需创建一个并在构造函数中提供上下文和类，并将数据放在相同的intent中。 ShowVideo活动对您的第二个Intent一无所知。您可以使用“VideoLink”键保存额外内容，并希望使用“ShowVideo”键获得额外的功能。你必须使用相同的密钥，否则你将无法获得任何东西。该错误是因为您的额外内容为空，这可能是因为您没有向您的真实意图添加任何数据。您必须为类和数据使用一个intent。

onCreate应如下所示：

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


//Video-Link abfangen
Bundle extras = getIntent().getExtras();
String videoLink = extras.getString("VideoLink");

....

}

其次，我会在ShowVideo活动中为你的额外名字制作一个静态常量。所以在ShowVideo的顶部添加

public static final String EXTRA_VIDEO_LINK = "VideoLink";

而不是你的看法中的“VideoLink”而是你写的更多内容ShowVideo.EXTRA_VIDEO_LINK 这样可以防止您无意中拥有不同的密钥。

Answer 4

试试这个：

final Intent Showvideo = new Intent(test2.this, ShowVideo.class);
Showvideo.putExtra("VideoLink", link);
startActivity(Showvideo);

通过接收意图强制关闭错误

4 个答案: