Question

我有一个更新我的eclipse和sdk到一个更新的版本。现在的证据是当我创建一个新的android项目而不是只有1个java和1个xml文件时我也创建了1个片段。我的问题是为什么我在appcompat_v7中收到错误。这是因为appcompat_v7，因为我的代码没有错误，为什么我无法运行应用程序。我不知道为什么我有这个android.content.ContextWrapper.getResources(ContextWrapper.java:89)，因为我的代码最多只有87行。

04-07 04:36:57.490: E/AndroidRuntime(1176): FATAL EXCEPTION: main
04-07 04:36:57.490: E/AndroidRuntime(1176): Process: com.afield.numpad, PID: 1176
04-07 04:36:57.490: E/AndroidRuntime(1176): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.afield.numpad/com.afield.numpad.MainActivity}: java.lang.NullPointerException
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.os.Handler.dispatchMessage(Handler.java:102)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.os.Looper.loop(Looper.java:136)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.ActivityThread.main(ActivityThread.java:5017)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at java.lang.reflect.Method.invokeNative(Native Method)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at java.lang.reflect.Method.invoke(Method.java:515)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at dalvik.system.NativeStart.main(Native Method)
04-07 04:36:57.490: E/AndroidRuntime(1176): Caused by: java.lang.NullPointerException
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.content.ContextWrapper.getResources(ContextWrapper.java:89)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.view.ContextThemeWrapper.getResources(ContextThemeWrapper.java:78)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at com.afield.numpad.MainActivity.<init>(MainActivity.java:25)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at java.lang.Class.newInstanceImpl(Native Method)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at java.lang.Class.newInstance(Class.java:1208)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
04-07 04:36:57.490: E/AndroidRuntime(1176):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
04-07 04:36:57.490: E/AndroidRuntime(1176):     ... 11 more

MainActivity

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.GridView;
import android.widget.Toast;
import android.os.Build;
import android.app.Activity;
import android.widget.AdapterView;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
    GridView gridView;

     final String[] numbers = new String[] { 
            "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "0",getResources().getString(R.string.dialogc)};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        gridView = (GridView) findViewById(R.id.gridView1);

        ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, numbers);

        gridView.setAdapter(adapter);

        gridView.setOnItemClickListener(new OnItemClickListener() {
            public void onItemClick(AdapterView<?> parent, View v,
                int position, long id) {
               Toast.makeText(getApplicationContext(),
                ((TextView) v).getText(), Toast.LENGTH_SHORT).show();
            }
        });
        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container,
                    false);
            return rootView;
        }
    }

}

red 我的错误是numpad文件夹和appcompat_v7文件夹中的红色感叹号

更新logcat

04-07 05:08:33.670: E/AndroidRuntime(1279): FATAL EXCEPTION: main
04-07 05:08:33.670: E/AndroidRuntime(1279): Process: com.afield.numpad, PID: 1279
04-07 05:08:33.670: E/AndroidRuntime(1279): java.lang.NoClassDefFoundError: android.support.v7.appcompat.R$styleable
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.support.v7.app.ActionBarActivityDelegate.onCreate(ActionBarActivityDelegate.java:104)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.support.v7.app.ActionBarActivityDelegateICS.onCreate(ActionBarActivityDelegateICS.java:57)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:98)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at com.afield.numpad.MainActivity.onCreate(MainActivity.java:18)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.Activity.performCreate(Activity.java:5231)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.os.Handler.dispatchMessage(Handler.java:102)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.os.Looper.loop(Looper.java:136)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at android.app.ActivityThread.main(ActivityThread.java:5017)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at java.lang.reflect.Method.invokeNative(Native Method)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at java.lang.reflect.Method.invoke(Method.java:515)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-07 05:08:33.670: E/AndroidRuntime(1279):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

引起：java.lang.NullPointerException 04-07 04：36：57.490： E / AndroidRuntime（1176）：at android.content.ContextWrapper.getResources（ContextWrapper.java:89）

您正在使用此

getResources().getString(R.string.dialogc)

在onCreate之外。将其移至onCreate。

http://developer.android.com/reference/android/content/Context.html#getResources()

public abstract Resources getResources ()

Added in API level 1
Return a Resources instance for your application's package.

getResources()是Context的一种方法，一旦创建了Activity，就可以使用上下文。

String[] numbers;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
numbers = new String[] { 
    "1", "2", "3", "4", "5",
    "6", "7", "8", "9", "0",getResources().getString(R.string.dialogc)};

编辑：

java.lang.NoClassDefFoundError： android.support.v7.appcompat.R $设置样式

您尚未正确引用AppCompat。因此问题

选中使用资源添加库。

https://developer.android.com/tools/support-library/setup.html

并按照相应的步骤进行操作

Answer 2

在numbers方法中初始化onCreate()数组，如下所示......

String[] numbers;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    numbers = new String[] { 
        "1", "2", "3", "4", "5",
        "6", "7", "8", "9", "0",getResources().getString(R.string.dialogc)};

}

Answer 3

在eclipse中创建每个新项目时，它还会创建一个appcompat_v7。必须存在以运行代码。请检查它是否存在。

Answer 4

getResources（）。getString（R.string.dialogc）这一行应该在onCreate（）

中

Answer 5

试试这个：

在活动中;

this.getResources().getString(R.string.dialogc);

外部活动;

contextObject.getResources().getString(R.string.dialogc);

像这样：

String[] numbers;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    numbers = new String[] { 
        "1", "2", "3", "4", "5",
        "6", "7", "8", "9", "0",this.getResources().getString(R.string.dialogc)};

}

Answer 6

您是否更新了支持库

Goto Window >> Android SDK Manager >> Extras >> Android Support Library

更新它

以及getResources().getString(R.string.dialogc)此行应位于onCreate（）

中

android appcompat_v7错误logcat

6 个答案: