Question

I have tried many things and keep receiving a crash error on my Android app. My app is a simple webwrapper app using the webview function. Basically, I have webview displaying a website that has a mobile site. What I am trying to do is make it so that

1. back button will take the user back to the previous screen
2. back button on the app (which I put in the layout), will also take the user to the previous screen.
3. I also want the home button on the phone to go back to the home screen and exit the app completely.
4. Lastly, the mobile app has external links that should be going into a browser and not staying within the app (example: visit full site).

Below is my code, any help for any of the 1-4 questions would be helpful! :-)! If you need to see my XML dont hesitate to ask.

package com.example.envision;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.webkit.DownloadListener;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ImageView;
import android.widget.ProgressBar;

public class Envision extends Activity {
/** back button functionality NOT WORKING CAUSES A CRASH
WebView webview;
@Override
   public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(event.getAction() == KeyEvent.ACTION_DOWN) {
            switch(keyCode)
            {
            case KeyEvent.KEYCODE_BACK:
                if(webview.canGoBack() == true){
                    webview.goBack();
                } else {
                    finish();
                }
                return true;
            }
        }
        return super.onKeyDown(keyCode, event);
    } */

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_envision);

WebView webview = (WebView) findViewById(R.id.webView1);

WebSettings websettings = webview.getSettings();

websettings.setJavaScriptEnabled(true);
websettings.setSaveFormData(false);
websettings.setSavePassword(false);

webview.loadUrl("http://envisionfinancial.ca/m/");
webview.setHorizontalScrollBarEnabled(false);
webview.setScrollBarStyle(View.SCROLLBARS_OUTSIDE_OVERLAY);
webview.setBackgroundColor(128);

webview.setWebViewClient(new EnvisionWebViewClient());

webview.setDownloadListener(new DownloadListener() {
    public void onDownloadStart(String url, String userAgent,
            String contentDisposition, String mimetype,
            long contentLength) {
        Intent intent = new Intent(Intent.ACTION_VIEW);
        intent.setData(Uri.parse(url));
        startActivity(intent);
        }


});

}

public void visible(){

WebView webview = (WebView) findViewById(R.id.webView1);

ImageView logo = (ImageView) findViewById(R.id.imageView1);

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

webview.setVisibility(10);

logo.setVisibility(0);

bar.setVisibility(0);

}

public void unvisible(){

WebView webview = (WebView) findViewById(R.id.webView1);

ImageView logo = (ImageView) findViewById(R.id.imageView1);

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

webview.setVisibility(0);

logo.setVisibility(10);

bar.setVisibility(10);

}


private class EnvisionWebViewClient extends WebViewClient {
@Override
public boolean shouldOverrideUrlLoading(WebView webview, String url){
    webview.loadUrl(url);
    return true;
}


@Override
public void onReceivedError(WebView view, int errorCode,
    String description, String failingUrl) {
// TODO Auto-generated method stub
view.loadUrl("http://envisionfinancial.ca/m/");
}

@Override
public void onPageStarted(WebView view, String url, Bitmap favicon) {

visible();

}

@Override
public void onPageFinished(WebView view, String url) {

unvisible();

}

}
/** exits the app?? review */
public void finishActivity(View v) {
finish();

}
}

Answer 1

Are you getting a NullPointerException in onKeyDown? That is because you do not assign the WebView to the instance variable:

webview = (WebView) findViewById(R.id.webView1);

The back functionality can be implemented like this:

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