当我用一个带有 webview 的片段添加选项卡布局时，应用程序停止了

Posted 2023-02-24

【中文标题】当我用一个带有 webview 的片段添加选项卡布局时，应用程序停止了

【英文标题】：Application getting stopped when i added tab layout with one fragment with webview

【发布时间】：2018-02-20 05:46:54

【问题描述】：

LOGCAT 错误报告

02-20 10:46:13.344 7295-7295/seacoders.abhilash.bogguru E/dalvikvm: Could not find class 'android.support.v4.widget.DrawerLayout$1', referenced from method android.support.v4.widget.DrawerLayout.<init>

02-20 10:46:13.352 7295-7295/seacoders.abhilash.bogguru E/dalvikvm: Could not find class 'android.view.WindowInsets', referenced from method android.support.v4.widget.DrawerLayout.onDraw

02-20 10:46:13.354 7295-7295/seacoders.abhilash.bogguru E/dalvikvm: Could not find class 'android.view.WindowInsets', referenced from method android.support.v4.widget.DrawerLayout.onMeasure

02-20 10:46:13.356 7295-7295/seacoders.abhilash.bogguru E/dalvikvm: Could not find class 'android.view.WindowInsets', referenced from method android.support.v4.widget.DrawerLayout.onMeasure

02-20 10:46:13.424 7295-7295/seacoders.abhilash.bogguru E/dalvikvm: Could not find class 'android.graphics.drawable.RippleDrawable', referenced from method android.support.v7.widget.AppCompatImageHelper.hasOverlappingRendering

02-20 10:46:14.055 7295-7295/seacoders.abhilash.bogguru E/AndroidRuntime: FATAL EXCEPTION: main
                                                                          java.lang.NullPointerException
                                                                              at seacoders.abhilash.bogguru.HomeFragment$MyWebViewClient.onPageStarted(HomeFragment.java:55)
                                                                              at android.webkit.CallbackProxy.handleMessage(CallbackProxy.java:331)
                                                                              at android.os.Handler.dispatchMessage(Handler.java:107)
                                                                              at android.os.Looper.loop(Looper.java:194)
                                                                              at android.app.ActivityThread.main(ActivityThread.java:5371)
                                                                              at java.lang.reflect.Method.invokeNative(Native Method)
                                                                              at java.lang.reflect.Method.invoke(Method.java:525)
                                                                              at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
                                                                              at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
                                                                              at dalvik.system.NativeStart.main(Native Method)

FRAGMENTHOME.java

package seacoders.abhilash.bogguru;

import android.graphics.Bitmap;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;
import android.widget.TextView;

public class HomeFragment extends Fragment 
    private WebView wv;
    private TextView txt;
    ProgressBar pbar;

    public static final String TITLE = "Home";

    public static HomeFragment newInstance() 

        return new HomeFragment();
    

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, Bundle savedInstanceState) 
        //return inflater.inflate(R.layout.fragment_home, container, false);
        View v=inflater.inflate(R.layout.fragment_home, container, false);
        wv = (WebView)v.findViewById(R.id.webview);
        wv.loadUrl("http://www.google.com");
        WebSettings webSettings = wv.getSettings();
        webSettings.setjavascriptEnabled(true);
        pbar = (ProgressBar) container.findViewById(R.id.pg1);
        txt = (TextView) container.findViewById(R.id.txtload);
        wv.setWebViewClient(new MyWebViewClient());
        return v;
    

    public class MyWebViewClient extends WebViewClient 

        public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) 
            wv.loadUrl("file:///android_asset/error.html");
        

        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) 
            super.onPageStarted(view, url, favicon);
            System.out.println("loading... please wait");
            pbar.setVisibility(View.VISIBLE);
            txt.setVisibility(View.VISIBLE);
        

        @Override
        public void onPageFinished(WebView view, String url) 
            System.out.println("finished loading");
            pbar.setVisibility(View.GONE);
            txt.setVisibility(View.GONE);
        
    

【问题讨论】：

What is a NullPointerException, and how do I fix it?的可能重复

也显示你的 xml ..

第 55 行的内容。可能 pbar 或 txt 是 null 。将视图 ID 与布局 xml 匹配。

pbar & txt 不是 null 已经在 fragment_home.xml 中声明

【参考方案1】：

下面几行的问题

   pbar = (ProgressBar) container.findViewById(R.id.pg1);
   txt = (TextView) container.findViewById(R.id.txtload);

你在container上被称为findViewById方法，你应该调用v而不是container。

解决方案

   pbar = (ProgressBar) v.findViewById(R.id.pg1);
   txt = (TextView) v.findViewById(R.id.txtload);

谢谢

【讨论】：

非常感谢