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javascript - HTML5 Canvas 支持和 Android Webview

转载 作者:塔克拉玛干 更新时间:2023-11-03 00:12:56 29 4
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我需要在我的应用程序中绘制图表。为此,我使用 RGraph (http://www.rgraph.net/);它允许使用 Javascript 绘制交互式图表。我将我的 javascript 代码放在应用程序 Assets 中的 HTML 文档中,然后从 ViewPager 中的 fragment 调用它。

这是 HTML 和 javascript 代码:

<meta http-equiv="content-type" content="text/html; charset=utf-8" />

<html>
<head>
<script src="./libraries/RGraph.common.core.js" ></script>
<script src="./libraries/RGraph.common.dynamic.js" ></script>
<script src="./libraries/RGraph.common.tooltips.js" ></script>
<script src="./libraries/RGraph.common.effects.js" ></script>
<script src="./libraries/RGraph.pie.js" ></script>
</head>
<body background="../transparent.png">

<canvas id="cvs" width="420" height="400">[No canvas support]</canvas>

<script>

function CreateGradient (obj, color)
{
return RGraph.RadialGradient(obj, 200, 150, 95, 200, 150, 125, color, color)
}

function isCanvasSupported(){
var test_canvas = document.createElement("canvas");
var canvascheck=(test_canvas.getContext) ? true : false ;
return canvascheck;
}
window.onload = function ()
{
if(isCanvasSupported)
DrawPieChart();
else
document.write("hheheheheh");
}


function DrawPieChart ()
{
var canvas = document.getElementById('cvs');
var ctx = canvas.getContext('2d');
var pie = new RGraph.Pie('cvs', [2,3,6,7,82]);
pie.Set('chart.colors', [
CreateGradient(pie, '#580600'),
CreateGradient(pie, '#AEAEAE'),
CreateGradient(pie, '#860100'),
CreateGradient(pie, '#C7C7C7'),
CreateGradient(pie, '#A70000')
]);
pie.Set('chart.labels.sticks', true);
pie.Set('chart.labels.sticks.length', 5);
pie.Set('chart.tooltips', ['Autres',
'Italie',
'Royaume-Uni',
'Espagne',
'France']);
pie.Set('chart.labels', ['2%','3%','6%','7%','82%']);
pie.Set('chart.radius', 150);
pie.Set('chart.shadow', true);
pie.Set('chart.shadow.offsetx', 0);
pie.Set('chart.shadow.offsety', 0);
pie.Set('chart.shadow.blur', 25);
pie.Draw();
}
</script>
</body>
</html>

这是 fragment 的代码:

@Override
public void onActivityCreated(Bundle savedInstanceState) {
mWebView = (WebView)getActivity().findViewById(R.id.group_fragment_one_webView);
mWebView.setFocusable(false);
mWebView.loadUrl("file:///android_asset/graphs/graph1.html");
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setDefaultZoom(ZoomDensity.FAR);
mWebView.getSettings().setDefaultFontSize(24);
mWebView.getSettings().setBuiltInZoomControls(false);
mWebView.setBackgroundColor(0);
mWebView.setHorizontalScrollBarEnabled(false);
mWebView.setVerticalScrollBarEnabled(false);
mWebView.getSettings().setSupportZoom(false);
mWebView.getSettings().setRenderPriority(RenderPriority.HIGH);

String TAG = "HTML 5";
WebSettings ws = mWebView.getSettings();
ws.setJavaScriptEnabled(true);
ws.setAllowFileAccess(true);


if (Build.VERSION.SDK_INT>=Build.VERSION_CODES.ECLAIR) {
try {
Method m1 = WebSettings.class.getMethod("setDomStorageEnabled", new Class[]{Boolean.TYPE});
m1.invoke(ws, Boolean.TRUE);

Method m2 = WebSettings.class.getMethod("setDatabaseEnabled", new Class[]{Boolean.TYPE});
m2.invoke(ws, Boolean.TRUE);

Method m3 = WebSettings.class.getMethod("setDatabasePath", new Class[]{String.class});
m3.invoke(ws, "/data/data/" + getActivity().getApplicationContext().getPackageName() + "/databases/");

Method m4 = WebSettings.class.getMethod("setAppCacheMaxSize", new Class[]{Long.TYPE});
m4.invoke(ws, 1024*1024*8);

Method m5 = WebSettings.class.getMethod("setAppCachePath", new Class[]{String.class});
m5.invoke(ws, "/data/data/" + getActivity().getApplicationContext().getPackageName() + "/cache/");

Method m6 = WebSettings.class.getMethod("setAppCacheEnabled", new Class[]{Boolean.TYPE});
m6.invoke(ws, Boolean.TRUE);

Log.d(TAG, "Enabled HTML5-Features");
}
catch (NoSuchMethodException e) {
Log.e(TAG, "Reflection fail", e);
}
catch (InvocationTargetException e) {
Log.e(TAG, "Reflection fail", e);
}
catch (IllegalAccessException e) {
Log.e(TAG, "Reflection fail", e);
}

}


mTextView1 = (TextView)getActivity().findViewById(R.id.group_fragment_one_textview1);
mTextView1.setText(getActivity().getResources().getString(R.string.group_fragment_one_text1));
Spannable spanSize = new SpannableString(mTextView1.getText());
spanSize.setSpan(new RelativeSizeSpan(2.0f),
0,
mTextView1.getText().toString().indexOf("millions"),
Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

mTextView1.setText(spanSize);
Spannable colorSpan = new SpannableString(mTextView1.getText());
colorSpan.setSpan(new ForegroundColorSpan(getActivity().getResources().getColor(R.color.red_ribbon)),
0,
mTextView1.getText().toString().indexOf("millions"),
Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
mTextView1.setText(colorSpan);
mTextView1.setTypeface(Utils.getTextFont(getActivity().getApplicationContext()));


mTextView2 = (TextView)getActivity().findViewById(R.id.group_fragment_one_textview2);
mTextView2.setText(getActivity().getResources().getString(R.string.group_fragment_one_text2));
spanSize = new SpannableString(mTextView2.getText());
spanSize.setSpan(new RelativeSizeSpan(2.0f),
0,
mTextView2.getText().toString().indexOf("du chiffre"),
Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);

mTextView2.setText(spanSize);
colorSpan = new SpannableString(mTextView2.getText());
colorSpan.setSpan(new ForegroundColorSpan(getActivity().getResources().getColor(R.color.red_ribbon)),
0,
mTextView2.getText().toString().indexOf("du chiffre"),
Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
mTextView2.setText(colorSpan);
mTextView2.setTypeface(Utils.getTextFont(getActivity().getApplicationContext()));


super.onActivityCreated(savedInstanceState);
}

它在模拟器和 Eclipse 浏览器上运行良好...但是当我想在智能手机上看到它时,我遇到了 Canvas 的错误。有时图表会正确显示,有时会显示“不支持 Canvas ”。在ViewPager中,只有fragment n、fragment n-1和n+1被同时实例化。当用户在另一个 fragment 上滚动时,其他 fragment 被实例化。因此,每次用户滚动时,都会加载 HTML。有时支持 Canvas ,有时不支持...

我试图在 javascript 中获得对 Canvas 的支持,但它总是返回支持 Canvas ,但事实并非如此......

有什么想法吗?

最佳答案

尝试在 onResume() 方法上加载 webview:

@Override
public void onResume(){

mWebView.loadUrl("file:///android_asset/graphs/graph1.html");
super.onResume();

}

关于javascript - HTML5 Canvas 支持和 Android Webview,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12246113/

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