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Android WebView-线程

android multithreading webview

Android WebView-线程,android,multithreading,webview,Android,Multithreading,Webview,[最后编辑。仍不确定给出的答案应如何实施。] 我很难理解Android应用程序中线程的问题。该应用程序基本上是一个html网页，我需要在webview和android应用程序之间来回切换以进行加载和保存。我希望该网页能够处理所有消息（因为我有一个很好的统一css-为了简单起见，我只在下面使用alert） 单击“保存”等按钮时出现的主要错误： W/WebView: java.lang.Throwable: A WebView method was called on thread 'JavaBri

[最后编辑。仍不确定给出的答案应如何实施。]

我很难理解Android应用程序中线程的问题。该应用程序基本上是一个html网页，我需要在webview和android应用程序之间来回切换以进行加载和保存。我希望该网页能够处理所有消息（因为我有一个很好的统一css-为了简单起见，我只在下面使用alert）

单击“保存”等按钮时出现的主要错误：

W/WebView: java.lang.Throwable: A WebView method was called on thread 'JavaBridge'. All WebView methods must be called on the same thread. (Expected Looper Looper (main, tid 1) {527e3354} called on Looper (JavaBridge, tid 109) {527ece88}, FYI main Looper is Looper (main, tid 1) {527e3354})
           at android.webkit.WebView.checkThread(WebView.java:2072)
           at android.webkit.WebView.evaluateJavascript(WebView.java:903)
           at com.example.jon.androidhtmltemplate.WebAppInterface.save(WebAppInterface.java:116)
           at com.android.org.chromium.base.SystemMessageHandler.nativeDoRunLoopOnce(Native Method)
           at com.android.org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:24)
           at android.os.Handler.dispatchMessage(Handler.java:102)
           at android.os.Looper.loop(Looper.java:136)
           at android.os.HandlerThread.run(HandlerThread.java:61)
W/System.err: java.lang.RuntimeException: java.lang.Throwable: A WebView method was called on thread 'JavaBridge'. All WebView methods must be called on the same thread. (Expected Looper Looper (main, tid 1) {527e3354} called on Looper (JavaBridge, tid 109) {527ece88}, FYI main Looper is Looper (main, tid 1) {527e3354})
W/System.err:     at android.webkit.WebView.checkThread(WebView.java:2082)
              at android.webkit.WebView.evaluateJavascript(WebView.java:903)
W/System.err:     at com.example.jon.androidhtmltemplate.WebAppInterface.save(WebAppInterface.java:116)
              at com.android.org.chromium.base.SystemMessageHandler.nativeDoRunLoopOnce(Native Method)
              at com.android.org.chromium.base.SystemMessageHandler.handleMessage(SystemMessageHandler.java:24)
              at android.os.Handler.dispatchMessage(Handler.java:102)
              at android.os.Looper.loop(Looper.java:136)
              at android.os.HandlerThread.run(HandlerThread.java:61)
          Caused by: java.lang.Throwable: A WebView method was called on thread 'JavaBridge'. All WebView methods must be called on the same thread. (Expected Looper Looper (main, tid 1) {527e3354} called on Looper (JavaBridge, tid 109) {527ece88}, FYI main Looper is Looper (main, tid 1) {527e3354})
              at android.webkit.WebView.checkThread(WebView.java:2072)
W/System.err:   ... 7 more
I/chromium: [INFO:CONSOLE(21)] "Uncaught Error: Error calling method on NPObject.", source: file:///android_asset/www/index.html (21)
I/Choreographer: Skipped 135 frames!  The application may be doing too much work on its main thread.
I/Choreographer: Skipped 58 frames!  The application may be doing too much work on its main thread.
我在启动时收到类似这样的奇怪警告（它们是否与我有关）

这是我的密码

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
    <android.support.constraint.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">

    <WebView
        android:id="@+id/webView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</android.support.constraint.ConstraintLayout>
webappinterface.java

package com.example.jon.androidhtmltemplate;

import android.content.Context;
import android.os.Build;
import android.os.Environment;
import android.webkit.WebView;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

// This is my class to handle interaction between my webpage and the Android app
public class WebAppInterface {
    Context mContext;
    WebView webview;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context c, WebView w) {
        mContext = c;
        webview = w;
    }

    /* Checks if external storage is available for read and write */
    public boolean isExternalStorageWritable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state)) {
            return true;
        }
        return false;
    }

    /* Checks if external storage is available to at least read */
    public boolean isExternalStorageReadable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state) ||
                Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
            return true;
        }
        return false;
    }

    @android.webkit.JavascriptInterface
    public void load(boolean isLoadExternal){
        String ret, script;

        ret = loadLocalExternal(isLoadExternal);

        script = "javascript:CallbackAndroidLoad(\"" + ret + "\")";
        if (Build.VERSION.SDK_INT >= 19 /*Might need 21*/) {
            webview.evaluateJavascript(script, null);
        }else {
            webview.loadUrl(script);
        }
    }

    @android.webkit.JavascriptInterface
    public String loadLocalExternal(boolean isExternal) {
        int length;
        String ret = "";
        File path = isExternal ? mContext.getExternalFilesDir(null) : mContext.getFilesDir();
        String filename = "myappsavefile.glf";
        File file = new File(path, filename);
        FileInputStream in;
        byte[] bytes;

        try {
            length = (int) file.length();
            bytes = new byte[length];
            in = new FileInputStream(file);
            in.read(bytes);
            in.close();
            ret = new String(bytes);
        } catch (Exception e) {
            ret = "";
        }

        return ret;
    }

    @android.webkit.JavascriptInterface
    public void save(boolean saveLocal, boolean saveExternal, String fileContent){
        boolean ret = true;
        String script;

        if(ret && saveLocal && !saveLocalExternal(false, fileContent + " local")) ret = false;
        if(ret && saveExternal && !saveLocalExternal(true, fileContent + " external")) ret = false;

        script = "javascript: CallbackAndroidSave(\"" + (ret ? "true" : "false") + "\")";
        if (Build.VERSION.SDK_INT >= 19 /*Might need 21*/) {
            webview.evaluateJavascript(script, null);
        }else {
            webview.loadUrl(script);
        }
    }

    @android.webkit.JavascriptInterface
    public boolean saveLocalExternal(boolean isExternal, String fileContent) {
        boolean ret = true;
        File path = isExternal ? mContext.getExternalFilesDir(null) : mContext.getFilesDir();
        String filename = "chartmygolf.glf";
        File file = new File(path, filename);
        FileOutputStream outputStream;

        try {
            outputStream = mContext.openFileOutput(filename, Context.MODE_PRIVATE);
            outputStream.write(fileContent.getBytes());
            outputStream.close();
        } catch (Exception e) {
            //e.printStackTrace();
            ret = false;
        }
        return ret;
    }
}
index.html

<!DOCTYPE html>
<html>
<head>
    <title>Page Title</title>
</head>
<body>

<h1>This is a Heading</h1>
<p>This is a paragraph with very interesting content.</p>
<p id="id">This is another paragraph.</p>
<button onclick="save()">Save</button>
<button onclick="loadLocal()">Load Local</button>
<button onclick="loadExternal()">Load External</button>

</body>
<script>
var isAndroid = /Android/i.test(navigator.userAgent);
document.getElementById("id").innerHTML = "This is on Android";

function save(){
    Android.save(true, true, "File Contents 1");
};

function loadLocal(){
    Android.load(false);
};

function loadExternal(){
    Android.load(true);
};

// ---

function CallbackAndroidLoad(fileContents){
    document.getElementById("id").innerHTML = fileContents.length > 0 ? "Error: Load Fail" : ("Contents: " + fileContents);
};

function CallbackAndroidSave(isSuccess){
    alert(isSuccess ? "Success" : "Failure");
};

</script>
</html>
Q:什么是
activityObj
？它来自哪里？如果必须通过调用函数传递，我该怎么做

Q:我在代码中的注释是否正确：
这是函数中唯一一个包含回调的位，因此我需要单独在这一位上执行特殊操作

JavascriptInterface
方法在后台线程上调用，而不是在UI线程上调用。在处理UI时，需要使用主UI线程

由于您是在单独的类中执行它，因此需要传递
Activity
对象，然后在所有
JavascriptInterface
方法中：

将
WebAppInterface
类更改如下：

public class WebAppInterface {
    Activity activityObj;
    WebView webview;

    /** Instantiate the interface and set the context */
    WebAppInterface(Activity activityObj, WebView w) {
        mContext = c;
        this.activityObj = activityObj;
    }   
    ...
}

activityObj.runOnUiThread(new Runnable() {
    @Override
    public void run() {
        if (Build.VERSION.SDK_INT >= 19 /*Might need 21*/) {
                webview.evaluateJavascript(script, null);
        }else {
            webview.loadUrl(script);
        }
    }
});
全文如下：

public class WebAppInterface {
    Activity activityObj;
    WebView webview;

    /** Instantiate the interface and set the context */
    WebAppInterface(Activity activityObj, WebView w) {
        mContext = c;
        this.activityObj = activityObj;
    }   
    ...
}

activityObj.runOnUiThread(new Runnable() {
    @Override
    public void run() {
        if (Build.VERSION.SDK_INT >= 19 /*Might need 21*/) {
                webview.evaluateJavascript(script, null);
        }else {
            webview.loadUrl(script);
        }
    }
});
或者，您可以实现一些回调接口，并在活动本身中执行如下操作：

public interface Callback {
    void loadLocalExternal(boolean isExternal);
    //define other methods.
}
MainActivity.java

public class MainActivity extends AppCompatActivity implements Callback{

     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView webview = (WebView)findViewById(R.id.webView);
        webview.getSettings().setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient());
        webview.loadUrl("file:///android_asset/www/index.html");

        webview.addJavascriptInterface(new WebAppInterface(this, this), "Android");
    }

    @Override
    public void loadLocalExternal(boolean isExternal){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //Do your action here
            }
        });
    }

}

public class WebAppInterface {
    Context mContext;
    private final Callback callback;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context c, Callback callback) {
        mContext = c;
        this.callback = callback;
    }
    @android.webkit.JavascriptInterface
    public String loadLocalExternal(boolean isExternal) {
        callback.loadLocalExternal(isExternal);
    }
    ...
}
WebAppInterface.java

public class MainActivity extends AppCompatActivity implements Callback{

     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView webview = (WebView)findViewById(R.id.webView);
        webview.getSettings().setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient());
        webview.loadUrl("file:///android_asset/www/index.html");

        webview.addJavascriptInterface(new WebAppInterface(this, this), "Android");
    }

    @Override
    public void loadLocalExternal(boolean isExternal){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //Do your action here
            }
        });
    }

}

public class WebAppInterface {
    Context mContext;
    private final Callback callback;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context c, Callback callback) {
        mContext = c;
        this.callback = callback;
    }
    @android.webkit.JavascriptInterface
    public String loadLocalExternal(boolean isExternal) {
        callback.loadLocalExternal(isExternal);
    }
    ...
}

JavascriptInterface
方法在后台线程上调用，而不是在UI线程上调用。在处理UI时，需要使用主UI线程

由于您是在单独的类中执行它，因此需要传递
Activity
对象，然后在所有
JavascriptInterface
方法中：

将
WebAppInterface
类更改如下：

public class WebAppInterface {
    Activity activityObj;
    WebView webview;

    /** Instantiate the interface and set the context */
    WebAppInterface(Activity activityObj, WebView w) {
        mContext = c;
        this.activityObj = activityObj;
    }   
    ...
}

activityObj.runOnUiThread(new Runnable() {
    @Override
    public void run() {
        if (Build.VERSION.SDK_INT >= 19 /*Might need 21*/) {
                webview.evaluateJavascript(script, null);
        }else {
            webview.loadUrl(script);
        }
    }
});
全文如下：

public class WebAppInterface {
    Activity activityObj;
    WebView webview;

    /** Instantiate the interface and set the context */
    WebAppInterface(Activity activityObj, WebView w) {
        mContext = c;
        this.activityObj = activityObj;
    }   
    ...
}

activityObj.runOnUiThread(new Runnable() {
    @Override
    public void run() {
        if (Build.VERSION.SDK_INT >= 19 /*Might need 21*/) {
                webview.evaluateJavascript(script, null);
        }else {
            webview.loadUrl(script);
        }
    }
});
或者，您可以实现一些回调接口，并在活动本身中执行如下操作：

public interface Callback {
    void loadLocalExternal(boolean isExternal);
    //define other methods.
}
MainActivity.java

public class MainActivity extends AppCompatActivity implements Callback{

     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView webview = (WebView)findViewById(R.id.webView);
        webview.getSettings().setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient());
        webview.loadUrl("file:///android_asset/www/index.html");

        webview.addJavascriptInterface(new WebAppInterface(this, this), "Android");
    }

    @Override
    public void loadLocalExternal(boolean isExternal){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //Do your action here
            }
        });
    }

}

public class WebAppInterface {
    Context mContext;
    private final Callback callback;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context c, Callback callback) {
        mContext = c;
        this.callback = callback;
    }
    @android.webkit.JavascriptInterface
    public String loadLocalExternal(boolean isExternal) {
        callback.loadLocalExternal(isExternal);
    }
    ...
}
WebAppInterface.java

public class MainActivity extends AppCompatActivity implements Callback{

     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        WebView webview = (WebView)findViewById(R.id.webView);
        webview.getSettings().setJavaScriptEnabled(true);
        webview.setWebChromeClient(new WebChromeClient());
        webview.loadUrl("file:///android_asset/www/index.html");

        webview.addJavascriptInterface(new WebAppInterface(this, this), "Android");
    }

    @Override
    public void loadLocalExternal(boolean isExternal){
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                //Do your action here
            }
        });
    }

}

public class WebAppInterface {
    Context mContext;
    private final Callback callback;

    /** Instantiate the interface and set the context */
    WebAppInterface(Context c, Callback callback) {
        mContext = c;
        this.callback = callback;
    }
    @android.webkit.JavascriptInterface
    public String loadLocalExternal(boolean isExternal) {
        callback.loadLocalExternal(isExternal);
    }
    ...
}
谢谢你的回复，但我有点困惑。这就是为什么我花了一点时间来回应。我理解你在UI线程上做这些事情的意思。这是有道理的，但我仍然有点不确定如何实施它。由于我的问题中有很多代码需要您的回答，我已经更新了我的原始问题，其中引用了您的答案。这是在底部开始：编辑（由萨加尔建议）：感谢萨加尔添加到您的答案，它帮助了我很多。从您在答案中添加的内容来看，WebAppInterface的函数构造函数似乎正在从上下文转换为活动。我想我需要上下文来做我以后想做的其他事情，所以我保留了mContext作为上下文，并进行了动态转换
（（Activity）mContext）.runOnUiThread（newrunnable（）
。这似乎很有效。因此，你的回答大大增加了我对Android编程的了解。@倒带没有问题。实际上，你不需要将对象作为上下文，你只需将contextObj替换为ActivityObj，因为在层次结构中，
Activity
扩展了
Context
。但其他方法是不可能的。如果e只需传递应用程序上下文，而不是
活动。此
，然后是
（（活动）mContext）
将导致崩溃。感谢您的回复，但我有点困惑。这就是我花了一点时间来回复的原因。我理解您关于在UI线程上执行这些操作的说法。这是有道理的，但我仍然有点不确定如何实现它。因为我对您的回复提出的问题中有很多代码，我已经更新了我的o参考你答案的原始问题。它在底部开始：编辑（如Sagar所建议）：感谢Sagar为您的答案添加内容，这对我帮助很大。从您在答案中添加的内容来看，WebAppInterface的函数构造函数似乎正在从上下文转换为活动。我想我需要上下文来完成我以后想做的其他事情，所以我保留了McContext作为上下文，并进行了动态转换
(（活动）mContext.runOnUiThread（新的Runnable（）
。这似乎很有效。因此，你的回答大大增加了我对Android编程的了解。@倒带没有问题。实际上，你不需要将对象作为上下文，你只需将contextObj替换为ActivityObj，因为在层次结构中，
Activity
扩展了
Context
。但其他方法是不可能的。如果e只需传递应用程序上下文，而不是
活动。这
，然后
（（活动）mContext）
将导致崩溃。