以'正道'创建属于自己的Web APP

不走旁门左道了，今天记录一个以正规方法创建web app的方法，本屌作为一名CV工程师（Ctrl+C and Ctrl+V）来说，代码什么意思不求甚解，只要知道这样创建就行了。

第一步：安装Android Studio，大小约1.6G，预计安装完成需要6小时。as编译器有坑哦，(特么不能删除项目  )

第二步：一路按照提示创建一个新的项目，如图：

接下来是重点：主类文件MainActivity.java中添加如下代码：

package com.example.xu.youyax;

import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.Uri;
import android.os.Build;
import android.os.Environment;
import android.os.Handler;
import android.provider.MediaStore;
import android.support.v4.widget.SwipeRefreshLayout;
import android.support.v7.app.AlertDialog;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.KeyEvent;
import android.webkit.JsResult;
import android.webkit.ValueCallback;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Toast;

import java.io.File;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private WebView webview;
    private SwipeRefreshLayout swipeLayout;
    private final static int FILECHOOSER_RESULTCODE = 5*1024;
    private static final String TAG = MainActivity.class.getSimpleName();
    private String mCM;
    private ValueCallback<Uri> mUM;
    private ValueCallback<Uri[]> mUMA;
    private final static int FCR=1;
    private long exitTime = 0;
    private String MYURL = "http://bbs.youyax.com/";
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent intent){
        super.onActivityResult(requestCode, resultCode, intent);
        if(Build.VERSION.SDK_INT >= 21){
            Uri[] results = null;
            //Check if response is positive
            if(resultCode== Activity.RESULT_OK){
                if(requestCode == FCR){
                    if(null == mUMA){
                        return;
                    }
                    if(intent == null){
                        //Capture Photo if no image available
                        if(mCM != null){
                            results = new Uri[]{Uri.parse(mCM)};
                        }
                    }else{
                        String dataString = intent.getDataString();
                        if(dataString != null){
                            results = new Uri[]{Uri.parse(dataString)};
                        }
                    }
                }
            }
            mUMA.onReceiveValue(results);
            mUMA = null;
        }else{
            if(requestCode == FCR){
                if(null == mUM) return;
                Uri result = intent == null || resultCode != RESULT_OK ? null : intent.getData();
                mUM.onReceiveValue(result);
                mUM = null;
            }
        }
    }
    @SuppressLint({"SetJavaScriptEnabled", "WrongViewCast"})
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        webview = (WebView)findViewById(R.id.webview);
        WebSettings webSettings = webview.getSettings();
        //设置WebView属性，能够执行Javascript脚本    
        webSettings.setJavaScriptEnabled(true);
        //设置可以访问文件  
        webSettings.setAllowFileAccess(true);
        //设置支持缩放  
        //webSettings.setBuiltInZoomControls(true);
        //
        webview.setWebChromeClient(new WebChromeClient(){
            @Override
            //Alert
            public boolean onJsAlert(WebView view,String url,String message,final JsResult result){
                AlertDialog.Builder b = new AlertDialog.Builder(MainActivity.this);
                b.setTitle("友情提示 : ");
                b.setMessage(message);
                b.setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        result.confirm();
                    }
                });
                b.setCancelable(false);
                b.create().show();
                return true;
            }
            //For Android 4.1+
            public void openFileChooser(ValueCallback<Uri> uploadMsg, String acceptType, String capture){
                mUM = uploadMsg;
                Intent i = new Intent(Intent.ACTION_GET_CONTENT);
                i.addCategory(Intent.CATEGORY_OPENABLE);
                i.setType("image/*");
                MainActivity.this.startActivityForResult(Intent.createChooser(i, "File Chooser"), MainActivity.FCR);
            }
            //For Android 5.0+
            public boolean onShowFileChooser(
                    WebView webView, ValueCallback<Uri[]> filePathCallback,
                    WebChromeClient.FileChooserParams fileChooserParams){
                if(mUMA != null){
                    mUMA.onReceiveValue(null);
                }
                mUMA = filePathCallback;
                Intent takePictureIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
                if(takePictureIntent.resolveActivity(MainActivity.this.getPackageManager()) != null){
                    File photoFile = null;
                    try{
                        photoFile = createImageFile();
                        takePictureIntent.putExtra("PhotoPath", mCM);
                    }catch(IOException ex){
                        Log.e(TAG, "Image file creation failed", ex);
                    }
                    if(photoFile != null){
                        mCM = "file:" + photoFile.getAbsolutePath();
                        takePictureIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile));
                    }else{
                        takePictureIntent = null;
                    }
                }
                Intent contentSelectionIntent = new Intent(Intent.ACTION_GET_CONTENT);
                contentSelectionIntent.addCategory(Intent.CATEGORY_OPENABLE);
                contentSelectionIntent.setType("image/*");
                Intent[] intentArray;
                if(takePictureIntent != null){
                    intentArray = new Intent[]{takePictureIntent};
                }else{
                    intentArray = new Intent[0];
                }

                Intent chooserIntent = new Intent(Intent.ACTION_CHOOSER);
                chooserIntent.putExtra(Intent.EXTRA_INTENT, contentSelectionIntent);
                chooserIntent.putExtra(Intent.EXTRA_TITLE, "Image Chooser");
                chooserIntent.putExtra(Intent.EXTRA_INITIAL_INTENTS, intentArray);
                startActivityForResult(chooserIntent, FCR);
                return true;
            }
            //设置进度条
            @Override
            public void onProgressChanged(WebView view, int newProgress) {
                if(newProgress == 100){
                    //隐藏进度条
                    swipeLayout.setRefreshing(false);
                }else if(!swipeLayout.isRefreshing()){
                    //swipeLayout.setRefreshing(true);
                }
            }
        });
        //下拉刷新
        swipeLayout = (SwipeRefreshLayout)findViewById(R.id.swipe_container);
        swipeLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
             @Override
             public void onRefresh() {
                 //刷新
                 swipeLayout.setRefreshing(true);
                 webview.loadUrl(webview.getUrl());
             }});
        //首次启动刷新页面
        /*swipeLayout.post(new Runnable() {
            @Override
            public void run() {
                swipeLayout.setRefreshing(true);
                webview.loadUrl(webview.getUrl());
            }
        });*/
        swipeLayout.setColorSchemeResources(android.R.color.holo_blue_light,
                android.R.color.holo_red_light,
                android.R.color.holo_orange_light,
                android.R.color.holo_green_light);
        //加载需要显示的网页    
        webview.loadUrl(MYURL);
        //取消滚动条
        webview.setScrollBarStyle(webview.SCROLLBARS_OUTSIDE_OVERLAY);
        //设置Web视图    
        webview.setWebViewClient(new webViewClient());
    }
    // Create an image file
    private File createImageFile() throws IOException{
        @SuppressLint("SimpleDateFormat") String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "img_"+timeStamp+"_";
        File storageDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        return File.createTempFile(imageFileName,".jpg",storageDir);
    }
    @Override
    //设置回退
    //覆盖Activity类的onKeyDown(int keyCoder,KeyEvent event)方法
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if ((keyCode == KeyEvent.KEYCODE_BACK) && webview.canGoBack() && !webview.getUrl().equals(MYURL)){
            webview.goBack(); //goBack()表示返回WebView的上一页面
            return true;
        }else {
            if(System.currentTimeMillis() - exitTime > 2000) {
                Toast.makeText(this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
                exitTime = System.currentTimeMillis();
                return true;
            }else{
                finish();
                System.exit(0);
                android.os.Process.killProcess(android.os.Process.myPid());
                return false;
            }
            //finish();//结束退出程序
            //return false;
        }
    }

    //Web视图
    private class webViewClient extends WebViewClient {
        public boolean shouldOverrideUrlLoading(WebView view, String url) {
            view.loadUrl(url);
            return true;
        }
    }
}

　activity_main.xml代码：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <android.support.v4.widget.SwipeRefreshLayout
        android:id="@+id/swipe_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    <WebView
        android:id="@+id/webview"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />
    </android.support.v4.widget.SwipeRefreshLayout>
</LinearLayout>

　appsrcmain esvaluesstyles.xml设置成 NoActionBar

<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">

　　

appsrcmain
esvaluesstrings.xml
设置APP名字

<string name="app_name">优雅社区</string>

效果图：

总结：主程序里主要解决2个坑：
一个是webview不支持Alert
另一个是webview不支持input type=file