我在按音量按钮时出错

Question

我已经创建了一个webview应用程序。按音量键时，我的应用程序崩溃。这是logcat中的错误

W/ViewRootImpl[MainActivity]：由于没有窗口焦点而取消事件：KeyEvent{action=action\u UP，keyCode=keyCode\u VOLUME\u DOWN，scanCode=114，metaState=0，flags=0x28，repeatCount=0，eventTime=196583031，downTime=196582864，deviceId=9，source=0x101}

下面是我的Main Activity.java文件：

package app.freeairdrop.io;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Bundle;
import android.support.v4.widget.SwipeRefreshLayout;
import android.view.KeyEvent;
import android.view.Menu;
import android.view.View;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.ProgressBar;
public class MainActivity extends Activity{
    private ProgressBar progressBar;
    private WebView webView;
    private SwipeRefreshLayout mySwipeRefreshLayout;
    @SuppressLint("SetJavaScriptEnabled")
    @Override
    public void onCreate(Bundle savedInstanceState) {




        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        progressBar = (ProgressBar) findViewById(R.id.progressBar);
        progressBar.setMax(100);
        webView = (WebView) findViewById(R.id.webView);
        webView.setWebViewClient(new WebViewClientDemo());
        webView.setWebChromeClient(new WebChromeClientDemo());
        webView.getSettings().setJavaScriptEnabled(true);

        webView.getSettings().setJavaScriptCanOpenWindowsAutomatically(true);
        webView.getSettings().setPluginState(WebSettings.PluginState.ON);
        webView.getSettings().setMediaPlaybackRequiresUserGesture(false);

        webView.loadUrl("http://freeairdrop.io/");

        mySwipeRefreshLayout = (SwipeRefreshLayout)this.findViewById(R.id.swipeContainer);


        mySwipeRefreshLayout.setOnRefreshListener(
                new SwipeRefreshLayout.OnRefreshListener() {
                    @Override
                    public void onRefresh() {
                        webView.reload();
                        mySwipeRefreshLayout.setRefreshing(false);
                    }
                }
        );

    }






    private class WebViewClientDemo extends WebViewClient {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            Uri uri = Uri.parse(url);
            if (uri.getHost() != null && (url.startsWith("https://freeairdrop.io/") || url.startsWith("https://www.freeairdrop.io/"))) {
                return false;
            }

            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(url));
            view.getContext().startActivity(intent);
            return true;
        }
        @Override
        public void onPageFinished(WebView view, String url) {
            super.onPageFinished(view, url);
            progressBar.setVisibility(View.GONE);
            progressBar.setProgress(100);
        }

        @Override
        public void onPageStarted(WebView view, String url, Bitmap favicon) {
            super.onPageStarted(view, url, favicon);
            progressBar.setVisibility(View.VISIBLE);
            progressBar.setProgress(0);
        }
    }


    private class WebChromeClientDemo extends WebChromeClient {
        public void onProgressChanged(WebView view, int progress) {
            progressBar.setProgress(progress);
        }
    }
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
            webView.goBack();
            return true;
        }
        else {
            finish();
        }
        return super.onKeyDown(keyCode, event);
    }




    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        return true;
    }

    @Override
    // This method is used to detect back button
    public void onBackPressed() {
        if(webView.canGoBack()) {
            webView.goBack();
        } else {
            // Let the system handle the back button
            super.onBackPressed();
        }
    }
}

Answer 1

从这里删除调用完成（），

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
        webView.goBack();
        return true;
    }
    else {
        finish(); // Remove this, onBackPressed() should handle it.
    }
    return super.onKeyDown(keyCode, event);
}

Answer 2

使用以下方法将焦点添加到webview：

<WebView android:id="@+id/webview"
    android:layout_weight="1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:focusable="true"/>

或

webview.request焦点（View.FOCUS_DOWN|View.FOCUS_UP）；

Answer 3

Remove 
finish();

from here :
if ((keyCode == KeyEvent.KEYCODE_BACK) && webView.canGoBack()) {
            webView.goBack();
            return true;
        }
        else {
            finish();
        }