【发布时间】：2021-10-20 14:46:06
【问题描述】：
我想使用 Webview 呈现 html，但我不想显示内容。为此，我以编程方式创建一个 Webview 并加载 HTML。它几乎可以工作了。问题是我似乎无法设置 Webview 的尺寸，因此 HTML 以我想要的大小呈现。我正在使用 WebviewClient 拍摄 WebviewContent 的快照并将其转换为位图。
以下代码仅用于测试，并非我的最终意图。我根本不想显示内容，但这会测试功能，当用户点击打印按钮时会填充图像。我希望图像的宽度为 380（高度可以根据需要高）。图片非常小（87 x 144）。
我对以下代码有 2 个问题：
-
第一次运行时，快照总是抛出异常，指示位图尺寸必须> 0
-
在第二次尝试（以及后续尝试）时，生成的位图不是所需的尺寸。当然，缩放只会让情况变得更糟。
包 com.b2ps.htmlrender;
导入androidx.appcompat.app.AppCompatActivity；
导入 android.graphics.Bitmap; 导入android.graphics.Canvas； 导入android.graphics.Paint； 导入android.os.Bundle； 导入android.view.View； 导入 android.webkit.WebView； 导入 android.webkit.WebViewClient； 导入android.widget.Button； 导入android.widget.ImageView； 导入android.util.Log；
导入 java.io.BufferedReader; 导入 java.io.IOException； 导入 java.io.InputStreamReader;
/**
- 主要活动
*/ 公共类 MainActivity 扩展 AppCompatActivity {
private static final String TAG = "USDK"; private ImageView ImagePreview = null; private WebView mReceiptView = null; private WebViewClient mWebviewClient = null; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); WebView.enableSlowWholeDocumentDraw(); Button printBtn = ( Button )findViewById( R.id.btnPrint ); printBtn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { onPrintClicked(); } }); ImagePreview = ( ImageView )findViewById( R.id.imgPreview ); } private void onPrintClicked() { print(); } private void print() { mReceiptView = new WebView( this ); mWebviewClient = new SnapshotWebviewClient( this ); mReceiptView.setWebViewClient( mWebviewClient ); mReceiptView.setMinimumWidth( 380 ); mReceiptView.setMinimumHeight( 720 ); String receiptHtml = getHtml(); mReceiptView.loadData( receiptHtml, "text/html; charset=utf-8", "UTF-8" ); } protected String getHtml() { StringBuilder htmlStr = new StringBuilder(); BufferedReader reader = null; try { reader = new BufferedReader( new InputStreamReader( this.getAssets().open("Receipt2.html" ) ) ); // do reading, usually loop until end of file reading String mLine; while ((mLine = reader.readLine()) != null) { //process line htmlStr.append( mLine ); htmlStr.append( "\n" ); } } catch (IOException e) { //log the exception Log.e( TAG, "IO exception", e); } finally { if (reader != null) { try { reader.close(); } catch (IOException e) { //log the exception Log.e( TAG, "error closing stream", e ); } } } return htmlStr.toString(); } //--------------------------------------------------------------------------------------------- // #region SnapshotWebviewClient /** * SnapshotWeviewClient */ private static class SnapshotWebviewClient extends WebViewClient { private static final String TAG = "USDK"; private MainActivity mMainActivity; public SnapshotWebviewClient( MainActivity activity ) { mMainActivity = activity; } @Override public void onPageFinished(WebView view, String url) { // FYI anyone wanting to do this right, use webView.ScrollView.ContentSize.Height then // set the Frame of the webview. Works perfect! Log.i( TAG, "SnapshotWebviewClient.onPageFinished" ); super.onPageFinished( view, url ); try { // Thread.sleep( 25 ); // Bitmap bitmap = Bitmap.CreateBitmap( view.MeasuredWidth, view.ContentHeight, Bitmap.Config.Argb8888 ); // Canvas canvas = new Canvas( bitmap ); // Paint paint = new Paint(); // int iHeight = bitmap.Height; // canvas.DrawBitmap( bitmap, 0, iHeight, paint ); // view.Draw( canvas ); Bitmap bitmap = screenshot( view ); // bitmap = scaleToReceipt( bitmap, 380 ); Log.i( TAG, String.format( "Bitmap size: w(%d), h(%d)", bitmap.getWidth(), bitmap.getHeight() ) ); mMainActivity.ImagePreview.setImageBitmap( bitmap ); // save bitmap to file java.io.File externalPath = view.getContext().getExternalFilesDir( null ); java.io.File filePath = new java.io.File( externalPath, "Receipt.png" ); java.io.FileOutputStream stream = new java.io.FileOutputStream( filePath ); bitmap.compress( Bitmap.CompressFormat.PNG, 100, stream ); stream.close(); Log.i( TAG, "WebViewClient.PrintToBitmap" ); } catch ( Exception printErr ) { Log.e( TAG, "PrintWebView: "+printErr.toString(), printErr ); } } private Bitmap screenshot(android.webkit.WebView webView ) { webView.measure( View.MeasureSpec.makeMeasureSpec( 0, View.MeasureSpec.UNSPECIFIED ), android.view.View.MeasureSpec.makeMeasureSpec( 0, View.MeasureSpec.UNSPECIFIED ) ); Log.i( TAG, String.format( "webView dimensions1: w(%d), h(%d)", webView.getMeasuredWidth(), webView.getMeasuredHeight() ) ); webView.layout( 0, 0, webView.getMeasuredWidth(), webView.getMeasuredHeight() ); Log.i( TAG, String.format( "webView dimensions2: w(%d), h(%d)", webView.getMeasuredWidth(), webView.getMeasuredHeight() ) ); webView.setDrawingCacheEnabled( true ); webView.buildDrawingCache(); Bitmap bitmap = Bitmap.createBitmap( webView.getMeasuredWidth(), webView.getMeasuredHeight(), Bitmap.Config.ARGB_8888 ); Log.i( TAG, String.format( "HtmlBmp: w(%d), h(%d)", bitmap.getWidth(), bitmap.getHeight() ) ); Canvas canvas = new Canvas( bitmap ); Paint paint = new Paint(); int iHeight = bitmap.getHeight(); canvas.drawBitmap( bitmap, 0, iHeight, paint ); webView.draw( canvas ); return bitmap; } private Bitmap scaleToReceipt( Bitmap bmp, int printWidth ) { double scale = (( double )(printWidth - 1) / ( double )bmp.getWidth()); int w = ( int )(bmp.getWidth() * scale); int h = ( int )(bmp.getHeight() * scale); Log.i( TAG, String.format( "Scale Bmp: W(%d), H(%d)", w, h ) ); return Bitmap.createScaledBitmap( bmp, w, h, true ); } } // #endregion SnapshowWebviewClient //---------------------------------------------------------------------------------------------}
这是布局 XML
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:gravity="center"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintTop_toTopOf="parent" >
<Button
android:id="@+id/btnPrint"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Print" />
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ImageView
android:id="@+id/imgPreview"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</ScrollView>
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
【问题讨论】：
-
所以我解决了我的一个问题。我现在可以得到一个缩放到正确大小的位图。而不是： mReceiptView.setMinimumWidth( 380 ); mReceiptView.setMinimumHeight(720);使用：mReceiptView.layout(0, 0, 380, 720);当其他问题解决时，我会设置答案。在此调用的第一次迭代中，我仍然得到 0 x 0 的位图大小。并且间歇性地。当我调试并设置断点时，它发生的较少。因此，似乎存在一些时间问题。但我在 GUI 线程上做所有事情。