Android WebView：ProgressBar未显示（使用Google的教程）

Question

在WebView中加载网页时，不会显示进度条。我的XML代码段：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity"    >

    <ProgressBar
        style="?android:attr/progressBarStyleHorizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/progressBar"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <WebView
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/webView"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

我的MainActivity.java代码段：

public class Main1Activity extends ActionBarActivity
{
    private WebView webView;

    public void onCreate( Bundle savedInstanceState) {


        getWindow().requestFeature(Window.FEATURE_PROGRESS);

        super.onCreate(savedInstanceState);

        webView = new WebView(this);
        setContentView(webView);

        webView.getSettings().setJavaScriptEnabled(true);

        final Activity activity = this;
        webView.setWebChromeClient(new WebChromeClient() {
            public void onProgressChanged(WebView view, int progress) {
                // Activities and WebViews measure progress with different scales.
                // The progress meter will automatically disappear when we reach 100%
                activity.setProgress(progress * 100);
            }
        });
        webView.setWebViewClient(new WebViewClient() {
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
                Toast.makeText(activity, "Oh no! " + description, Toast.LENGTH_SHORT).show();
            }
        });

        webView.loadUrl("http://developer.android.com/");
    }

    // Go back to previous upon clicking back button
    // instead of closing app.
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack())
        {
            webView.goBack();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();


        return super.onOptionsItemSelected(item);
    }


}

我已经检查了Stackoverflow上关于此的所有资源并发布了这个因为我找不到任何解决方案。起初这应该是非常容易的，但是这需要超过5天而且还在计算中。

Answer 1

我认为您正在尝试混合两个不同的ProgressBar实现，第一个使用getWindow().requestFeature(Window.FEATURE_PROGRESS);，第二个使用ProgressBar定义到您的Main布局中。我认为最好的选择是在布局中使用ProgressBar。

因此，您需要更改一下代码，使用onPageStarted()显示ProgressBar和onPageFinished()来隐藏它：

public class MainActivity extends ActionBarActivity
{
    private WebView webView;
    private ProgressBar progressBar;

    public void onCreate( Bundle savedInstanceState) {


        //getWindow().requestFeature(Window.FEATURE_PROGRESS); // You don´t need this!

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        progressBar = (ProgressBar)findViewById(R.id.progressBar);  

        /*webView = new WebView(this);
            setContentView(webView);*/ //Using this your WebView was covering all your screen :P!
        webView = (WebView)findViewById(R.id.webView);//Use the WebView defined in your layout.

        webView.getSettings().setJavaScriptEnabled(true);

        final Activity activity = this;
        webView.setWebChromeClient(new WebChromeClient() {
            public void onProgressChanged(WebView view, int progress) {
                // Activities and WebViews measure progress with different scales.
                // The progress meter will automatically disappear when we reach 100%
                activity.setProgress(progress * 100);
            }
        });
        webView.setWebViewClient(new WebViewClient() {
            public void onReceivedError(WebView view, int errorCode, String description, String failingUrl) {
                Toast.makeText(activity, "Oh no! " + description, Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                progressBar.setVisibility(View.VISIBLE);
                super.onPageStarted(view, url, favicon);
            }

            @Override
            public void onPageFinished(WebView view, String url) {
                progressBar.setVisibility(View.INVISIBLE);
                super.onPageFinished(view, url);
            }



        });

        webView.loadUrl("http://developer.android.com/");
    }

       // Go back to previous upon clicking back button
    // instead of closing app.
    public boolean onKeyDown(int keyCode, KeyEvent event)
    {
        if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack())
        {
            webView.goBack();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();


        return super.onOptionsItemSelected(item);
    }


}

你的布局也有所改变：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

  <ProgressBar
      android:id="@+id/progressBar"
      style="?android:attr/progressBarStyleHorizontal"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:indeterminate="true"
      android:visibility="visible" />

    <WebView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/webView"
        android:layout_below="@+id/progressBar"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true" />
</RelativeLayout>

5天还在数？没办法:)）