Question

我在logcat中遇到了这个错误

06-21 11:58:27.275: E/AndroidRuntime(404): java.lang.RuntimeException: Unable to start activity ComponentInfo{App.Biodata/App.Biodata.viewdata}: java.lang.NullPointerException
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.os.Looper.loop(Looper.java:123)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.ActivityThread.main(ActivityThread.java:4627)
06-21 11:58:27.275: E/AndroidRuntime(404):  at java.lang.reflect.Method.invokeNative(Native Method)
06-21 11:58:27.275: E/AndroidRuntime(404):  at java.lang.reflect.Method.invoke(Method.java:521)
06-21 11:58:27.275: E/AndroidRuntime(404):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
06-21 11:58:27.275: E/AndroidRuntime(404):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
06-21 11:58:27.275: E/AndroidRuntime(404):  at dalvik.system.NativeStart.main(Native Method)
06-21 11:58:27.275: E/AndroidRuntime(404): Caused by: java.lang.NullPointerException
06-21 11:58:27.275: E/AndroidRuntime(404):  at App.Biodata.viewdata.onCreate(viewdata.java:42)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-21 11:58:27.275: E/AndroidRuntime(404):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
06-21 11:58:27.275: E/AndroidRuntime(404):  ... 11 more

java文件：

package App.Biodata;

import java.util.ArrayList;
import java.util.HashMap;

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

import android.app.ListActivity;
import android.os.Bundle;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;


public class viewdata extends ListActivity {

private static String link_url = "http://10.0.2.2/biodatawebservice/view.php";

private static final String BIO_NAMA = "nama";
private static final String BIO_ALAMAT = "alamat";
private static final String BIO_TGLLAHIR = "tgl_lahir";
private static final String BIO_JK = "jk";
private static final String BIO_EMAIL = "email";    
private static final String BIO_PHONE = "phone";

JSONArray biodata = null;

ArrayList<HashMap<String, String>> daftar_biodata = new ArrayList<HashMap<String, String>>();

/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.viewdata);

    JSONParser jParser = new JSONParser();

    JSONObject json = jParser.AmbilJson(link_url);

    try {
        biodata = json.getJSONArray("biodata");

        for(int i = 0; i < biodata.length(); i++){
            JSONObject bio = biodata.getJSONObject(i);

            String nama = bio.getString(BIO_NAMA);
            String alamat = bio.getString(BIO_ALAMAT);
            String tgl_lahir = bio.getString(BIO_TGLLAHIR);
            String jk = bio.getString(BIO_JK);
            String email = bio.getString(BIO_EMAIL);
            String phone = bio.getString(BIO_PHONE);

            HashMap<String, String> map = new HashMap<String, String>();

            map.put(BIO_NAMA, nama);
            map.put(BIO_ALAMAT, alamat);
            map.put(BIO_TGLLAHIR, tgl_lahir);
            map.put(BIO_JK, jk);
            map.put(BIO_EMAIL, email);
            map.put(BIO_PHONE, phone);

            daftar_biodata.add(map);
        }
    } catch (JSONException e) {
        e.printStackTrace();
    }
    this.adapter_listview();
}       

private void adapter_listview() {
    // TODO Auto-generated method stub
    ListAdapter adapter = new SimpleAdapter(this, daftar_biodata,
            R.layout.list_data,
            new String[] {  BIO_NAMA, BIO_ALAMAT, BIO_TGLLAHIR, BIO_JK, BIO_EMAIL, BIO_PHONE}, new int[] {
                    R.id.txtNama, R.id.txtAlamat, R.id.txtTgllahir, R.id.txtJK, R.id.txtEmail,R.id.txtPhone});

    setListAdapter(adapter);
    ListView lv = getListView();


}

}

listactivity的xml文件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<ListView
    android:id="@android:id/list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >
</ListView>

</LinearLayout>

每个项目的xml：

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="10dp" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="5dp"
        android:text="Nama"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#FFF" />

    <TextView
        android:id="@+id/txtNama"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#333"
        android:text=" "
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="10dp" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="5dp"
        android:text="Alamat"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#FFF" />

    <TextView
        android:id="@+id/txtAlamat"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#333"
        android:text=" "
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="10dp" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="5dp"
        android:text="Tanggal Lahir"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#FFF" />

    <TextView
        android:id="@+id/txtTgllahir"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#333"
        android:text=" "
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="10dp" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="5dp"
        android:text="Jenis Kelamin"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#FFF" />

    <TextView
        android:id="@+id/txtJK"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#333"
        android:text=" "
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="10dp" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="5dp"
        android:text="Telepon"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#FFF" />

    <TextView
        android:id="@+id/txtPhone"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#333"
        android:text=" "
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>

<LinearLayout
    android:id="@+id/linearLayout1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:paddingBottom="10dp" >

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingTop="5dp"
        android:text="Email"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:textColor="#FFF" />

    <TextView
        android:id="@+id/txtEmail"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#333"
        android:text=" "
        android:textAppearance="?android:attr/textAppearanceMedium" />
</LinearLayout>


</LinearLayout>

我无法找到这个应用程序有什么问题，有人可以告诉我为什么这个应用程序强行关闭？我已经阅读了一些答案，告诉它xml布局文件有问题，但仍无法找到解决方案

提前感谢。

[解决]

非常感谢stackoverflow.com会员帮助我，问题是这个

biodata = json.getJSONArray（“biodata”）;

为null，因为我的php失败了。

Answer 1

json is null所以NPE.You无法从JsonParser获取JsonObject。

biodata = json.getJSONArray("biodata");//here json is null.

并检查您的json = jParser.AmbilJson(link_url);

并且在setAdapter之后没有使用ListView lv = getListView();到listview。

Answer 2

嗯，我认为你应该学会正确阅读日志。从logcat告诉您的内容中检测问题更为重要。所以你可以这样做：

首先，在IDE上启用行号。其次，看一下logcat中如何描述问题：

     java.lang.RuntimeException: Unable to start activity componentInfo{App.Biodata/App.Biodata.viewdata}: java.lang.NullPointerException

因此，在viewdata类中抛出了一个空指针异常。发生这种情况是因为您尝试从null对象访问方法。

第三，继续寻找问题的原因：

   Caused by: java.lang.NullPointerException   E/AndroidRuntime(404):  at App.Biodata.viewdata.onCreate(viewdata.java:42).

所以问题出在你的viewdata.java第42行。

Answer 3

我认为下面的行有错误。

ListView lv = getListView();

所以请在下面使用。

ListView lv = (ListView) findViewById(R.id.list);

lv = getListView();

Answer 4

您将活动扩展为List活动，并且您也尝试访问制造商的XML布局。所以删除你的setContentView（R.layout.viewdata）;

由于

Answer 5

你这里有错误

 biodata = json.getJSONArray("biodata");

你必须把条件

if(json!=null)
{
    biodata = json.getJSONArray("biodata");
}

您的jParser.AmbilJson(link_url);必须失败

Android Force关闭java.lang.NullPointerException

[解决]

5 个答案: