Android WebView专题

WebView 专题

第一个WebView程序：加载远程网址

Layout添加WebView组件；

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<WebView
        android:id="@+id/webView_first"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

初始化组件，加载Url;

java 复制代码

public class FirstWebViewActivity extends AppCompatActivity{

    private WebView webView_first;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_first_web_view);
        webView_first=findViewById(R.id.webView_first);
        webView_first.loadUrl("https://www.baidu.com/");
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        webView_first.removeAllViews();
        webView_first.destroy();
    }
}

Manifest文件添加网络访问权限

xml 复制代码

<uses-permission android:name="android.permission.INTERNET" />

出现错误：

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NetworkSecurityConfig   com.hymy.webviewstarter              D  No Network Security Config specified, using platform default
Denied starting an intent without a user gesture, URI

解决方法：

res/xml下添加 network_security_config.xml 文件：

xml 复制代码

<?xml version="1.0" encoding="utf-8"?>
<network-security-config> //默认配置：允许明文通信
    <base-config cleartextTrafficPermitted="true" />
</network-security-config>

在AndroidManifest.xml中引用

xml 复制代码

<application
        android:networkSecurityConfig="@xml/network_security_config"
        ...

出现错误：

访问bing.com无法加载封面图片：

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The resource xxx was preloaded using link preload but not used within a few seconds from the window's load event. Please make sure it has an appropriate `as` value and it is preloaded intentionally.

解决方法：

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webView_first=findViewById(R.id.webView_first);
//启用JavaScript
WebSettings webSettings = webView_first.getSettings();
webSettings.setJavaScriptEnabled(true);
webView_first.loadUrl("https://cn.bing.com/?mkt=zh-CN");

下载：在bing搜索网站首页，好看的壁纸，点击可以下载图片，将图片下载到 SD 卡下的Downloader目录下

参考：https://cloud.tencent.com/developer/article/1742327

将 JavaScript代码绑定到Android代码

js调用Android代码中的方法

新建 WebAppInterface 类

java 复制代码

/**
 * @Author : alex
 * @Date : on 2023/11/14 09:21.
 * @Description :描述
 */
public class WebAppInterface {
    Context mContext;

    /**
     * 初始化接口，并设置context
     * @param c
     */
    WebAppInterface(Context c){
        mContext=c;
    }

    /**
     * 在Web页面显示消息提示
     * @param toast
     */
    @JavascriptInterface
    public void showToast(String toast){
        Toast.makeText(mContext,toast,Toast.LENGTH_SHORT).show();
    }
}

webview 绑定接口：

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 webView_first.addJavascriptInterface(new WebAppInterface(this),"Android");

html代码示例：

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<!doctype html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Bootstrap demo</title>
    <link href="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.3.1/css/bootstrap.min.css" rel="stylesheet">
  </head>
  <body>
    <h1>Hello, world!</h1>
    <input type="button" value="Say hello" onClick="showAndroidToast('Hello Android!')" />
    <script src="https://cdn.bootcdn.net/ajax/libs/twitter-bootstrap/5.3.1/js/bootstrap.bundle.min.js"></script>
    <script type="text/javascript">
      function showAndroidToast(toast) {
            Android.showToast(toast);
      }
    </script>
  </body>
</html>

webview中的跳转连接

参考：https://www.digitalocean.com/community/tutorials/android-webview-example-tutorial

当 html 中有跳转链接的时候，可以直接阻止、选择性阻止在我们的App跳转、或者可以打开系统浏览器，加载外部链接。

java 复制代码

webView_first.setWebViewClient(new MyWebViewClient());

private class MyWebViewClient extends WebViewClient {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
        Log.i("FirstWebViewActivity",request.getUrl().getHost());
        if ("192.168.96.108".equals(request.getUrl().getHost())) {
            // This is my website, so do not override; let my WebView load the page
            return false;
        }
        // Otherwise, the link is not for a page on my site, so launch another Activity that handles URLs
        Intent intent = new Intent(Intent.ACTION_VIEW, request.getUrl());
        startActivity(intent);
        return true;
    }
}

webview加载本地网页，实现 sqlite 数据库增删改查

使用的库 gson:

groovy 复制代码

implementation 'com.google.code.gson:gson:2.8.5'

首先新建assets文件夹，android默认工程没有创建。

编写 DBHelper ，定义数据库名，在 onCreate 中初始化数据库：

java 复制代码

public class MyDatabaseHelper extends SQLiteOpenHelper {
    public static final String DATABASE_NAME = "student.db";
    public static final int DATABASE_VERSION =1;

    public MyDatabaseHelper(Context context){
        super(context,DATABASE_NAME,null,DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // 数据库首次创建时调用，执行创建表等语句
        // 创建student表
        db.execSQL("CREATE TABLE student (" +
                "id INTEGER PRIMARY KEY AUTOINCREMENT," +
                "name TEXT," +
                "age INTEGER," +
                "birth TEXT)");
        // 如果需要初始化数据可以在这里插入:
        db.execSQL("INSERT INTO student (name, age, birth) " +
                "VALUES ('张三', 18, '1980-01-01')");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // 数据库版本更新时调用

    }
}

然后定义 MyApplication，在程序启动的时候初始化数据库：

java 复制代码

public class MyApplication extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        //检测数据库是否存在，不存在则创建数据库
        Context context = getApplicationContext();
        MyDatabaseHelper dbHelper = new MyDatabaseHelper(context);
        SQLiteDatabase db = dbHelper.getWritableDatabase();
    }
}

定义数据增、查接口类，供H5中调用：

java 复制代码

public class JsDBInterface {
    private SQLiteDatabase db;
    public JsDBInterface(Context context){
        // 在构造函数中打开数据库
        MyDatabaseHelper helper = new MyDatabaseHelper(context);
        db = helper.getWritableDatabase();
    }

    /**
     * 插入数据
     * @param name
     * @param age
     * @param birth
     */
    @JavascriptInterface
    public void insertData(String name,int age,String birth){
        //检查参数
        if(name==null||name.isEmpty()){
            return;
        }
        //插入数据
        ContentValues values = new ContentValues();
        values.put("name",name);
        values.put("age",age);
        values.put("birth",birth);
        db.insert("student",null,values);
        Log.i("插入数据",name);
    }

    /**
     * 查询数据
     * @return
     */
    @JavascriptInterface
    public String getAllStudents(){
        List<Student> students = new ArrayList<>();
        //查询数据库中的所有学生
        Cursor cursor = db.query("student",null,null,null,null,null,null);
        //获取所有列
//        String[] cols = cursor.getColumnNames();
//        int nameIndex=-1;
        while (cursor.moveToNext()){
            int columnIndex1=cursor.getColumnIndex("id");
            int columnIndex2=cursor.getColumnIndex("name");
            int columnIndex3=cursor.getColumnIndex("age");
            int columnIndex4=cursor.getColumnIndex("birth");
            int id=0;String name="null";int age=0;String birth="0000-00-00";
            if(columnIndex1>=0){
                id = cursor.getInt(columnIndex1);
            }
            if(columnIndex2>=0){
                name=cursor.getString(columnIndex2);
            }
            if(columnIndex3>=0){
                age = cursor.getInt(columnIndex3);
            }
            if(columnIndex4>=0){
                birth=cursor.getString(columnIndex4);
            }

            Student stu = new Student(id,name,age,birth);
            students.add(stu);
        }
        cursor.close();
        Gson gson = new Gson();
        String json = gson.toJson(students);
        return json;
    }
}

数据实体类：

java 复制代码

public class Student {
    private int id;
    private String name;
    private int age;
    private String birth;

    public int getId() {
        return id;
    }

    public Student(int id,String name, int age, String birth) {
        this.id=id;
        this.name = name;
        this.age = age;
        this.birth = birth;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getBirth() {
        return birth;
    }

    public void setBirth(String birth) {
        this.birth = birth;
    }
}

在 Activity 中注册接口：

java 复制代码

webView.addJavascriptInterface(new JsDBInterface(MainActivity.this),"JsDBInterface");

加载本地网页：
private String localUrl="file:///android_asset/index.html";
webView_first.loadUrl(localUrl);

HTML 使用了vue，调用代码如下：

复制代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="./vue.min.js"></script>
</head>
<body>
    <div id="app">
        <h2>{{message}}</h2>
        <ul>
            <li v-for="user in users" :key="user.id">{{user.name}}</li>
        </ul>
        <button id="btnInsertStudent" onclick="addStudent()">新增学生</button>
        <button id="btnGetAllStudents" onclick="getAllStudent()">查询所有学生</button>
        <ul id='studentList'></ul>
    </div>
    <script>
        var app = new Vue({
            el:'#app',
            data(){
                return {
                    message:'Hello Vue!'
                }
            },
            mounted(){
            }
        })
        function addStudent(){
            JsDBInterface.insertData("小明",18,"2010-01-01");
            alert('添加成功')
        }
        function getAllStudent(){
            var data = JsDBInterface.getAllStudents();
            var students = JSON.parse(data);
            var studentTxt='';
            for(var i = 0; i < students.length; i++) {
                var stu = students[i];
                studentTxt += '<li>' + stu.name + ',' + stu.age + ',' + stu.birth + '</li>';
              }
              var ul = document.getElementById('studentList');
              ul.innerHTML = studentTxt;
        }
    </script>
</body>
</html>

结果：

webview h5 alert 不运行

参考：https://copyprogramming.com/howto/modify-alert-title-javascript-in-android-webview

最简单的处理方法是：添加下面的代码
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```
webView_first.setWebChromeClient(new WebChromeClient());
```

但是上面的标题会显示网址，可以用下面的方法进行修改：

java 复制代码

webView_first.setWebChromeClient(new WebChromeClient(){
    @Override
    public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
        AlertDialog dialog = new AlertDialog.Builder(view.getContext())
            .setTitle("提示")
            .setMessage(message)
            .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    // do nothing
                }
            }).create();
        dialog.show();
        result.confirm();
        return true;
    }
});

修改后：

此外如果对 alert, prompt, confirm统一进行修改，可以使用下面代码：

java 复制代码

webView_first.setWebChromeClient(new WebChromeClient(){
    @Override
    public boolean onJsAlert(WebView view, String url, String message, JsResult result) {
        new AlertDialog.Builder(view.getContext())
            .setTitle("alert")
            .setMessage(message)
            .setPositiveButton("确定", (DialogInterface dialog, int which) -> result.confirm())
            .setOnDismissListener((DialogInterface dialog) -> result.confirm())
            .create()
            .show();
        return true;
    }

    @Override
    public boolean onJsConfirm(WebView view, String url, String message, JsResult result) {
        new AlertDialog.Builder(view.getContext())
            .setTitle("confirm")
            .setMessage(message)
            .setPositiveButton("确定", (DialogInterface dialog, int which) -> result.confirm())
            .setNegativeButton("取消", (DialogInterface dialog, int which) -> result.cancel())
            .setOnDismissListener((DialogInterface dialog) -> result.cancel())
            .create()
            .show();
        return true;
    }

    @Override
    public boolean onJsPrompt(WebView view, String url, String message, String defaultValue, JsPromptResult result) {
        final EditText input = new EditText(view.getContext());
        input.setInputType(InputType.TYPE_CLASS_TEXT);
        input.setText(defaultValue);
        new AlertDialog.Builder(view.getContext())
            .setTitle("prompt")
            .setMessage(message)
            .setView(input)
            .setPositiveButton("确定", (DialogInterface dialog, int which) -> result.confirm(input.getText().toString()))
            .setNegativeButton("取消", (DialogInterface dialog, int which) -> result.cancel())
            .setOnDismissListener((DialogInterface dialog) -> result.cancel())
            .create()
            .show();
        return true;
    }
});