Android：WebView 应用程序在显示启动画面 3 秒后崩溃

Question

so I've decided to make an android application for my website (not many people read it, however I think it'll look good on my Ucas! My problem is that after the splash screen is displayed on my phone the app crashes, I'm quite new to android app development so I'm unsure about what I'm doing wrong.

I've uploaded my sourcecode on to Github so that you can have a better look at it!

Heres some of my code:

MainActivity.java

package com.alffiw.alffisblog;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.MenuItem;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;


public class MainActivity extends Activity {

    private WebView mWebView;
    ProgressBar progressBar;


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

        mWebView = (WebView) findViewById(R.id.activity_main_webview);

        progressBar = (ProgressBar) findViewById(R.id.progressBar1);

        WebSettings webSettings = mWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        mWebView.loadUrl("http://www.coderefer.com");
        mWebView.setWebViewClient(new HelloWebViewClient());


    }

    private class HelloWebViewClient extends WebViewClient{


        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) {
            // TODO Auto-generated method stub
            super.onPageStarted(view, url, favicon);
        }

        @Override
        public boolean shouldOverrideUrlLoading(WebView webView, String url)
        {
            webView.loadUrl(url);
            return true;
        }

        @Override
        public void onPageFinished(WebView view, String url) {
            // TODO Auto-generated method stub
            super.onPageFinished(view, url);

            progressBar.setVisibility(view.GONE);
        }

    }


    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event)
    { //if back key is pressed
        if((keyCode == KeyEvent.KEYCODE_BACK)&& mWebView.canGoBack())
        {
            mWebView.goBack();
            return true;

        }

        return super.onKeyDown(keyCode, event);

    }




    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.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();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void onBackPressed() {
        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(
                MainActivity.this);

        // set title
        alertDialogBuilder.setTitle("Exit");

        // set dialog message
        alertDialogBuilder
                .setMessage("Do you really want to exit?")
                .setCancelable(false)
                .setPositiveButton("Yes",new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog,int id) {
                        // if this button is clicked, close
                        // current activity
                        MainActivity.this.finish();
                    }
                })
                .setNegativeButton("No",new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog,int id) {
                        // if this button is clicked, just close
                        // the dialog box and do nothing
                        dialog.cancel();
                    }
                });

        // create alert dialog
        AlertDialog alertDialog = alertDialogBuilder.create();

        // show it
        alertDialog.show();
    }
}

SplashScreen.java

package com.alffiw.alffisblog;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

public class SplashScreen extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.splash);

        Thread timerThread = new Thread(){
            public void run(){
                try{
                    sleep(3000);
                }catch(InterruptedException e){
                    e.printStackTrace();
                }finally{
                    Intent intent = new Intent(SplashScreen.this,MainActivity.class);
                    startActivity(intent);
                }
            }
        };
        timerThread.start();
    }

    @Override
    protected void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        finish();
    }

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
    <RelativeLayout 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" tools:context=".MainActivity">

    <ProgressBar
        android:layout_centerHorizontal="true"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_gravity="center_vertical|center_horizontal"
        android:id="@+id/progressBar1"/>

    <TextView
        android:layout_below="@+id/progressBar1"
        android:layout_height="wrap_content"
        android:id="@+id/LoadingText"
        android:layout_width="fill_parent"
        android:text="Loading, Please Wait.."
        android:textSize="20sp"
        android:gravity="center_horizontal">
    </TextView>

    <WebView
        android:id="@+id/activity_main_webview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    </RelativeLayout>

content_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.alffiw.alffisblog.MainActivity"
    tools:showIn="@layout/activity_main">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />
</RelativeLayout>

splash.xml

<?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:background="@drawable/splash_image"
    android:orientation="vertical">

</LinearLayout>

AndroidManifest.xml

    <?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.alffiw.alffisblog">
    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >

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

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

        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="com.coderefer.androidsplashscreenexample.MAINACTIVITY" />

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

</manifest>

Thank you for any help in advance!

Answer 1

Instead of calling from thread use Handler

protected void onCreate(Bundle savedInstanceState) {

    //your stuff.....
    new android.os.Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            if (!isFinishing()) {//just to make sure user didn,t press back button
                Intent mainIntent = new Intent(Splashscreen.this, MainActivity.class);
                startActivity(mainIntent);
                finish();
            }
        }
    }, 3000);//waiting time

}

Answer 2

You can't call startActivity(intent) form inside the thread you've created. Firstly because startActivity(...) is a Context method and secondly, you need to execute this statement on the UI thread.

Try this:

@Override
protected void onCreate(Bundle savedInstanceState) {

    ...

    final Context activity = this;
    Thread timerThread = new Thread(new Runnable(
            public void run(){
                try{
                    sleep(3000);
                }catch(InterruptedException e){
                    e.printStackTrace();
                }finally{
                    activity.runOnUiThread(new Runnable() {
                        public void run(){
                            Intent intent = new Intent(SplashScreen.this,MainActivity.class);
                            activity.startActivity(intent);
                        }
                    });                       
                }
            }
    ));
    timerThread.start();