启用早在web视图按钮 [英] Enable back button in WebView
本文介绍了启用早在web视图按钮的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我刚开始使用Android SDK。我想使用的WebView只显示本地网络页面的简单应用程序。我已经用我发现在网络上的例子做出来。
I am just starting out with the Android SDK. I wanted to make a simple app with WebView that displays local web-pages only. I have used examples I have found on the net to make it.
该应用程序的工作好了，直到我想添加一个后退按钮。当手机后退按钮是pressed应用程序崩溃。
The app works just great, until I want to add a back-button. When the phones back-button is pressed the app crashes.
下面是我的 MainActivity.java
package com.hspd.avhor;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.webkit.WebView;
import android.webkit.WebViewClient;
public class MainActivity extends Activity {
WebView wv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WebView wv = (WebView)findViewById(R.id.hspd_webview);
wv.setWebViewClient(new WebViewClient() {
@Override
public boolean shouldOverrideUrlLoading(WebView view, String url){
view.loadUrl(url);
return true;
}
});
wv.loadUrl("file:///android_asset/one.htm");
}
@Override
public void onBackPressed()
{
if(wv.canGoBack())
wv.goBack();
else
super.onBackPressed();
}
@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;
}
}
和这里是我的 activity_main.xml
<ScrollView 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:fillViewport="true"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<WebView
android:id="@+id/hspd_webview"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
</ScrollView>
下面是我在错误的的logcat
04-22 17:48:06.953: W/dalvikvm(799): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
04-22 17:48:06.972: E/AndroidRuntime(799): FATAL EXCEPTION: main
04-22 17:48:06.972: E/AndroidRuntime(799): java.lang.NullPointerException
04-22 17:48:06.972: E/AndroidRuntime(799): at com.hspd.avhor.MainActivity.onKeyDown(MainActivity.java:41)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.view.KeyEvent.dispatch(KeyEvent.java:2609)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.app.Activity.dispatchKeyEvent(Activity.java:2375)
04-22 17:48:06.972: E/AndroidRuntime(799): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1847)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.view.ViewRootImpl.deliverKeyEventPostIme(ViewRootImpl.java:3701)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.view.ViewRootImpl.handleImeFinishedEvent(ViewRootImpl.java:3651)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.view.ViewRootImpl$ViewRootHandler.handleMessage(ViewRootImpl.java:2818)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.os.Handler.dispatchMessage(Handler.java:99)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.os.Looper.loop(Looper.java:137)
04-22 17:48:06.972: E/AndroidRuntime(799): at android.app.ActivityThread.main(ActivityThread.java:5041)
04-22 17:48:06.972: E/AndroidRuntime(799): at java.lang.reflect.Method.invokeNative(Native Method)
04-22 17:48:06.972: E/AndroidRuntime(799): at java.lang.reflect.Method.invoke(Method.java:511)
04-22 17:48:06.972: E/AndroidRuntime(799): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-22 17:48:06.972: E/AndroidRuntime(799): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-22 17:48:06.972: E/AndroidRuntime(799): at dalvik.system.NativeStart.main(Native Method)
在此先感谢：）
Thanks in advance :)
推荐答案
覆盖的onkeydown（PARAMS），检查关键pressed是后退按钮，检查web视图可以导航到previous页面，如果是的话naviagate至previous页面。如果没有网页，显示可以完成actiivty
Override onKeyDown(params), check if the key pressed is back button ,check if the webview can navigate to previous page, if so naviagate to previous page. If there is no web page to display you can finish the actiivty
您可以使用以下
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
//if Back key pressed and webview can navigate to previous page
webView.goBack();
// go back to previous page
return true;
}
else
{
finish();
// finish the activity
}
return super.onKeyDown(keyCode, event);
}
编辑：
在删除XML布局的滚动视图。请尝试以下
Remove the scrollview in xml layout. Try the below
<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"
tools:context=".MainActivity" >
<WebView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:id="@+id/wv"></WebView>
</LinearLayout>
编辑：2
下面是一种可行的样本。测试上三星Galaxy S3
Here's a sample that works. Tested on samsung galaxy s3
activtiy_main.xml
activtiy_main.xml
<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"
tools:context=".MainActivity" >
<WebView
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:id="@+id/wv"/>
</RelativeLayout>
MainActivity
MainActivity
public class MainActivity extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
webView = (WebView) findViewById(R.id.wv);
webView.getSettings().setJavaScriptEnabled(true);
webView.setWebChromeClient(new WebChromeClient() {
public void onProgressChanged(WebView view, int progress) {
MainActivity.this.setProgress(progress * 1000);
}
});
webView.setWebViewClient(new WebViewClient() {
public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
Toast.makeText(MainActivity.this, "Oh no! " + description, Toast.LENGTH_SHORT).show();
}
});
webView.loadUrl("http://slashdot.org/");
}
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
webView.goBack();
return true;
}
else
{
finish();
}
return super.onKeyDown(keyCode, event);
}
}
这篇关于启用早在web视图按钮的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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