Android WebView style background-color:transparent ignored on android 2.2

问题

I'm struggling to create a WebView with transparent background.

webView.setBackgroundColor(0x00FFFFFF);
webView.setBackgroundDrawable(myDrawable);

Then I load a html page with

<body style="background-color:transparent;" ...

The background color of the WebView is transparent but as soon as the page is loaded, it's overwritten by a black background from the html page. This only happens on android 2.2, it works on android 2.1.

So is there something to add in the html page code to make it really transparent ?

回答1:

This worked for me,

mWebView.setBackgroundColor(Color.TRANSPARENT);

回答2:

At the bottom of this earlier mentioned issue there is an solution. It's a combination of 2 solutions.

webView.setBackgroundColor(Color.TRANSPARENT);
webView.setLayerType(WebView.LAYER_TYPE_SOFTWARE, null);

When adding this code to the WebViewer after loading the url, it works (API 11+).

It even works when hardeware acceleration is ON

回答3:

I had the same issue with 2.2 and also in 2.3. I solved the problem by giving the alpa value in html not in android. I tried many things and what I found out is setBackgroundColor(); color doesnt work with alpha value. webView.setBackgroundColor(Color.argb(128, 0, 0, 0)); will not work.

so here is my solution, worked for me.

      String webData = StringHelper.addSlashes("<!DOCTYPE html><head> <meta http-equiv=\"Content-Type\" " +
      "content=\"text/html; charset=utf-8\"> </head><body><div style=\"background-color: rgba(10,10,10,0.5); " +
      "padding: 20px; height: 260px; border-radius: 8px;\"> $$$ Content Goes Here ! $$$ </div> </body></html>");

And in Java,

    webView = (WebView) findViewById(R.id.webview);
    webView.setBackgroundColor(0);
    webView.loadData(webData, "text/html", "UTF-8");

And here is the Output screenshot below.

回答4:

Actually it's a bug and nobody found a workaround so far. An issue has been created. The bug is still here in honeycomb.

Please star it if you think it's important : http://code.google.com/p/android/issues/detail?id=14749

回答5:

This is how you do it:

First make your project base on 11, but in AndroidManifest set minSdkVersion to 8

android:hardwareAccelerated="false" is unnecessary, and it's incompatible with 8

wv.setBackgroundColor(0x00000000);
if (Build.VERSION.SDK_INT >= 11) wv.setLayerType(WebView.LAYER_TYPE_SOFTWARE, null);

this.wv.setWebViewClient(new WebViewClient()
{
    @Override
    public void onPageFinished(WebView view, String url)
    {
        wv.setBackgroundColor(0x00000000);
        if (Build.VERSION.SDK_INT >= 11) wv.setLayerType(WebView.LAYER_TYPE_SOFTWARE, null);
    }
});

For safety put this in your style:

BODY, HTML {background: transparent}

worked for me on 2.2 and 4

回答6:

The most important thing was not mentioned.

The html must have a body tag with background-color set to transparent.

So the full solution would be:

HTML

    <body style="display: flex; background-color:transparent">some content</body>

Activity

    WebView wv = (WebView) findViewById(R.id.webView);
    wv.setBackgroundColor(0);
    wv.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
    wv.loadUrl("file:///android_asset/myview.html");

回答7:

below code works fine Android 3.0+ but when you try this code below android 3.0 then your app forcefully closed.

webView.setLayerType(WebView.LAYER_TYPE_SOFTWARE, null);

You try below code on your less then API 11.

webview.setBackgroundColor(Color.parseColor("#919191"));

you can also try below code which works on all API fine.

    webview.setBackgroundColor(Color.parseColor("#919191"));
    if (Build.VERSION.SDK_INT >= 11) {
        webview.setLayerType(WebView.LAYER_TYPE_SOFTWARE, null);
    }

above code use full for me.

回答8:

Try webView.setBackgroundColor(0);

回答9:

Following code work for me, though i have multiple webviews and scrolling between them is bit sluggish.

v.setBackgroundColor(Color.TRANSPARENT);
Paint p = new Paint();
v.setLayerType(LAYER_TYPE_SOFTWARE, p);

回答10:

Use this

WebView myWebView = (WebView) findViewById(R.id.my_web);

myWebView.setBackgroundColor(0);

回答11:

After trying everything given above. I found it doesn't matter either you specify
webView.setBackgroundColor(Color.TRANSPARENT) before or after loadUrl() /loadData().
The thing that matters is you should explicitly declare android:hardwareAccelerated="false" in the manifest.

Tested on IceCream Sandwich

回答12:

Just use these lines .....

webView.loadDataWithBaseURL(null,"Hello", "text/html", "utf-8", null);
webView.setBackgroundColor(0x00000000);

And remember a point that Always set background color after loading data in webview.

回答13:

If webview is scrollable:

Add this to the Manifest:
```
android:hardwareAccelerated="false"
```

Add the following to WebView in the layout:

android:background="@android:color/transparent"
android:layerType="software"

Add the following to the parents scroll view:
```
android:layerType="software"
```

回答14:

webView.setBackgroundColor(0x00000000);
webView.setLayerType(WebView.LAYER_TYPE_SOFTWARE, null);

this will definitely work.. set background in XML with Editbackground. Now that background will be shown

回答15:

set the bg after loading the html(from quick tests it seems loading the html resets the bg color.. this is for 2.3).

if you're loading the html from data you already got, just doing a .postDelayed in which you just set the bg(to for example transparent) is enough..

回答16:

Try webView.setBackgroundColor(Color.parseColor("#EDEDED"));

回答17:

I was trying to put a transparent HTML overlay over my GL view but it has always black flickering which covers my GL view. After several days trying to get rid of this flickering I found this workaround which is acceptable for me (but a shame for android).

The problem is that I need hardware acceleration for my nice CSS animations and so webView.setLayerType(View.LAYER_TYPE_SOFTWARE, null); is not an option for me.

The trick was to put a second (empty) WebView between my GL view and the HTML overlay. This dummyWebView I told to render in SW mode, and now my HTML overlays renders smooth in HW and no more black flickering.

I don't know if this works on other devices than My Acer Iconia A700, but I hope I could help someone with this.

public class MyActivity extends Activity {

    @Override
    protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);

        RelativeLayout layout = new RelativeLayout(getApplication());
        setContentView(layout);

        MyGlView glView = new MyGlView(this);

        RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MATCH_PARENT, RelativeLayout.LayoutParams.MATCH_PARENT);

        dummyWebView = new WebView(this);
        dummyWebView.setLayoutParams(params);
        dummyWebView.setLayerType(View.LAYER_TYPE_SOFTWARE, null);
        dummyWebView.loadData("", "text/plain", "utf8");
        dummyWebView.setBackgroundColor(0x00000000);

        webView = new WebView(this);
        webView.setLayoutParams(params);
        webView.loadUrl("http://10.0.21.254:5984/ui/index.html");
        webView.setBackgroundColor(0x00000000);


        layout.addView(glView);
        layout.addView(dummyWebView);
        layout.addView(webView);
    }
}

回答18:

This worked for me. try setting the background color after the data is loaded. for that setWebViewClient on your webview object like:

    webView.setWebViewClient(new WebViewClient(){

        @Override
        public void onPageFinished(WebView view, String url)
        {
            super.onPageFinished(view, url);
            webView.setBackgroundColor(Color.BLACK);
        }
    });

回答19:

Try out:

myWebView.setAlpha(0.2f);

回答20:

If nothing helps, then most probably you have fixed sized webView, change the width and height to wrap_content or match_parent, it should work. That worked for me when I tried to load a Gif.