Android Webview恢复后不显示html文件

Question

i have a webview that read HTML from SD-card and show it . when user open activity for first time, HTML file load correctly . but in some devices (such as Samsung galaxy series) if close activity and open it again, webview not show anything and is empty.

public class page extends Activity {

private static WebView web;
private  int path;

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

    Intent intent = getIntent();
    Bundle bundle = intent.getExtras(); 

    path = bundle.getInt("path");

    web = (WebView) findViewById(R.id.webview);
    web.setBackgroundColor(Color.TRANSPARENT);
    web.getSettings().setJavaScriptEnabled(true);
    web.setWebChromeClient(new WebChromeClient());

}

@Override
protected void onResume() {
    super.onResume();
    loadPage();

}

@Override
protected void onPause() {
    super.onPause();
    resetWebView();
} 

// becuase my webview play audio and if close activity sound also playing
private void resetWebView(){
    if (web != null){
        web.loadUrl("about:blank");
        web.destroy();
        web.destroyDrawingCache();
    }
}

private void loadPage(){

    String DIR =  Environment.getExternalStorageDirectory().getAbsolutePath()+"/myApp";

    if(path != null && web != null){
   switch (path) {
    case 3: {
        //   something like this 
        //  /storage/emulated/0/myApp/1/page_three.html/
        File file = new File(DIR+path+"page_three.html/");
        web.loadUrl("file://"+file);

    }
        break;
    case 2: {
        File file = new File(G.DIR_APP+path+"page_two.html/");
        web.loadUrl("file://"+file);
    }
        break;
    case 1: {
        File file = new File(G.DIR_APP+path+"page_one.html/");
        web.loadUrl("file://"+file);
    }
        break;
    case 0: {
        File file = new File(G.DIR_APP+path+"welcome.html/");
        web.loadUrl("file://"+file);
    }
        break;

    default:
        // do nothing
       }
   }
}

Answer 1

I had the same issue. This is for API 11 and greater. Adding webview.onResume() inside the onResume() function of fragment solved it for me.

So in your case:

public void onResume() {
    super.onResume();
    web.onResume();
}

Answer 2

If the activity is destroyed while paused, the Android system may re-create it when the user returns to it later. To ensure that the same data that was originally used to intialise the activity is restored, you need to override onSaveInstanceState() and onRestoreInstanceState() . I recommend this pattern - this will ensure the correct data is loaded for initial creation, resume after pause, recreation and resume after being destroyed, and when sent a new intent to load new data.

static final String ARG_PATH = "path";
protected Bundle bundle = null;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    bundle = getIntent().getExtras();
// perform other create-time initialisation here
}

@Override
protected void onNewIntent(Intent intent) {
    super.onNewIntent(intent);
    setIntent(intent);
    bundle = intent.getExtras();
}

@Override
protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    bundle = savedInstanceState;
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putInt(ARG_PATH, path);
}

@Override
protected void onResume() {
    super.onResume();
    if(bundle != null) {
        path = bundle.getInt(ARG_PATH);
        bundle = null;
        loadPage();
    } else
        web.onResume();
    // if bundle was already null, we were just resumed after pause, not destroyed so no reload is required.
}

@Override
protected void onPause() {
    web.onPause();    // pause any video etc.
    super.onPause();
}

Answer 3

当您离开活动时，请完成活动，因此，下次访问时，必须再次调用onCreate（Bundle savedInstanceState）方法。

Answer 4

我将以下代码添加到webview中并解决了问题

      webView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);