在创建 webview 时显示错误，如 'java.lang.NullPointerException' : Attempt to invoke interface method

Question

虽然创建 Android Webview 然后在运行之后生成太多 error.I 已经创建 class 像 mWebViewClient.java, Splash.java.

在MainActivity.java

package com.shopence.myapp;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.widget.ShareActionProvider;

public class MainActivity extends Activity {

private WebView mWebView;

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

    mWebView = (WebView) findViewById(R.id.activity_main_webview);
    WebSettings webSettings = mWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    mWebView.loadUrl("http://shopence.com/test/");
    mWebView.setWebViewClient(new com.shopence.myapp.mWebViewClient(){
        @Override
        public void onPageFinished(WebView mWebView, String url) {
            //hide loading image
            findViewById(R.id.progressBar1).setVisibility(View.GONE);
            /* show mWebView */
            findViewById(R.id.activity_main_webview).setVisibility(View.VISIBLE);
        }});
}

@Override
public void onBackPressed() {
    if(mWebView.canGoBack()) {
        mWebView.goBack();
    } else {
        super.onBackPressed();
    }
}


private ShareActionProvider mShareActionProvider;
@Override
public boolean onCreateOptionsMenu(Menu menu) {

    /** Inflating the current activity's menu with res/menu/items.xml */
    getMenuInflater().inflate(R.menu.menu_main, menu);

    /** Getting the actionprovider associated with the menu item whose id is share */
    mShareActionProvider = (ShareActionProvider) menu.findItem(R.id.share).getActionProvider();

    /** Setting a share intent */
    mShareActionProvider.setShareIntent(getDefaultShareIntent());

    return super.onCreateOptionsMenu(menu);

}

/** Returns a share intent */
private Intent getDefaultShareIntent(){
    Intent intent = new Intent(Intent.ACTION_SEND);
    intent.setType("text/plain");
    intent.putExtra(Intent.EXTRA_SUBJECT, "shopence.com");
    intent.putExtra(Intent.EXTRA_TEXT,"Welcome To Shopence");
    return intent;
}

}

在Splash.java

package com.shopence.myapp;

import android.annotation.SuppressLint;
import android.annotation.TargetApi;
import android.app.ActionBar;
import android.app.Activity;
import android.content.Intent;
import android.os.Build;
import android.os.Bundle;

@SuppressLint("NewApi")
public class Splash extends Activity {

    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash);

        ActionBar actionBar = getActionBar();
        assert actionBar != null;
        actionBar.hide();

        Thread t =new Thread(){
            public void run(){
                try{
                    sleep(10000);
                }catch(InterruptedException e){
                    e.printStackTrace();
                }finally{
                    Intent i =new Intent(Splash.this,MainActivity.class);
                    startActivity(i);
                }
            }
        };
        t.start();
    }
    @Override
    public void onPause(){
        super.onPause();
        finish();
    }

}

在运行代码之后显示

之类的错误

`'java.lang.NullPointerException' : Attempt to invoke interface method.`
 11-02 12:26:03.628    2245-2245/com.shopence.myapp E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.shopence.myapp, PID: 2245
java.lang.NullPointerException: Attempt to invoke interface method 'android.view.ActionProvider android.view.MenuItem.getActionProvider()' on a null object reference
        at com.shopence.myapp.MainActivity.onCreateOptionsMenu(MainActivity.java:55)
        at android.app.Activity.onCreatePanelMenu(Activity.java:2820)
        at com.android.internal.policy.impl.PhoneWindow.preparePanel(PhoneWindow.java:548)
        at com.android.internal.policy.impl.PhoneWindow.doInvalidatePanelMenu(PhoneWindow.java:917)
        at com.android.internal.policy.impl.PhoneWindow.run(PhoneWindow.java:258)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

activity_main.xml 文件喜欢

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
            xmlns:tools="http://schemas.android.com/tools"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:paddingLeft="@dimen/activity_horizontal_margin"
            android:paddingRight="@dimen/activity_horizontal_margin"
            android:paddingTop="@dimen/activity_vertical_margin"
            android:paddingBottom="@dimen/activity_vertical_margin"
            android:orientation="vertical"
            tools:context=".MainActivity">

<ProgressBar
    android:id="@+id/progressBar1"
    style="?android:attr/progressBarStyleSmall"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="161dp"
    android:indeterminate="false"
    android:layout_gravity="center"
    android:max="500"
    android:progress="0" />

<WebView
    android:id="@+id/activity_main_webview"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:visibility="gone" />

</LinearLayout>

AndoidManifest.xml 文件喜欢

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.shopence.myapp" >
<uses-permission android:name="android.permission.INTERNET" />
<application
    android:allowBackup="true"
    android:icon="@drawable/logo"
    android:label="@string/app_name"
    android:theme="@android:style/Theme.Holo.Light" >
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.DEFAULT" />s
        </intent-filter>
    </activity>

    <activity
        android:name=".Splash"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

 </application>

</manifest>

所以，请解决我的运行程序正确的问题

Answer 1

您的问题在这里：

mShareActionProvider = (ShareActionProvider) menu.findItem(R.id.share).getActionProvider();

menu.findItem(R.id.share) 是 null。确保 menu_main.xml

中有 R.id.share 菜单项

在创建 webview 时显示错误，如 'java.lang.NullPointerException' : Attempt to invoke interface method

While Creating webview it shown with error like 'java.lang.NullPointerException' : Attempt to invoke interface method

android

android-webview