Question

我有一个简单的webview来显示一个论坛..我需要“映射”后退按钮回到论坛的网页当然。我试着用这种方式但是给我一个致命的错误

public class MainActivity extends Activity
{
protected WebView webview;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    WebView webview = (WebView) findViewById(R.id.webview);
    WebSettings websettings = webview.getSettings();
    websettings.setJavaScriptEnabled(true);
    webview.setWebViewClient(new WebViewClient());
    if (savedInstanceState == null)
    {
        webview.loadUrl("http://www.proboards.com/");
    }

}

@Override
protected void onSavedInstanceState(Bundle outState) {
    //super.onSavedInstanceState(outState);

    webview.saveState(outState);
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    switch (keyCode) {
        case KeyEvent.KEYCODE_BACK:
            if(webview.canGoBack() == true)

                webview.goBack();
            else finish();
            break;

        default:
            break;
    }
    return super.onKeyDown(keyCode, event);
}
}

错误是onKeyDown第42行。

Answer 1

更改此

 WebView webview = (WebView) findViewById(R.id.webview); 
 // webview becomes local

要

 webview = (WebView) findViewById(R.id.webview);

您已宣布

 WebView webview;

作为班级成员

Answer 2

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    switch (keyCode) {
        case KeyEvent.KEYCODE_BACK:
            if(webview.canGoBack() == true)

                webview.goBack();
            else finish();
            return true;
    }
    return super.onKeyDown(keyCode, event);
}

这是：How to go back to previous page if back button is pressed in WebView?

的副本

在任何情况下，如果您处理了按键操作

，则必须返回true

Answer 3

试试这种方式

不要覆盖onKeyDown（）方法

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

如何实现webview中的后退按钮？

3 个答案: