Chrome 自定义标签会在浏览时预加载网页吗？

Posted 2023-02-19

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【中文标题】Chrome 自定义标签会在浏览时预加载网页吗？【英文标题】：Chrome Custom Tabs pre-load webpages while browsing? 【发布时间】：2016-09-21 20:23:14 【问题描述】：

我正在测试 Chrome 自定义标签。它应该预加载用户可能在后台点击的网页。这是通过调用

session.mayLaunchUrl(uri, null, null);

当 MainActivity 处于活动状态时，网页会很好地预加载，并且在启动 URL 时，网页会按预期快速加载。但是，我想在用户已经浏览时自动向用户提供其他网页（因此活动在后台）。然后，预加载网页似乎不再加快加载过程，即使正在加载新提供的网页，这也会缓慢发生。

我编写了一个小应用程序来演示这种行为。手动预加载和启动 URL 效果很好（因为活动是活动的，我想），自动在循环中提供新网页很慢（因为活动不活动并且 mayLaunchUrl 方法不能按预期工作）。

是否可以在用户已经浏览时使用预加载机制？如果是，如何？

我添加了 MainActivity 代码，如下示例：

public class MainActivity  extends AppCompatActivity 


private CustomTabsSession mCustomTabsSession;
private CustomTabsClient mClient;
private CustomTabsServiceConnection mConnection;

private EditText urlET;
private String TAG = "MainActivity";
private ArrayList<String> urlList;
private Thread cycleThread;


@Override
protected void onCreate(Bundle savedInstanceState) 
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Log.v("MainActivity", "onCreate");

    urlList = new ArrayList<>();
    urlList.add("http://www.google.com");
    urlList.add("https://github.com");
    urlList.add("http://***.com");
    urlList.add("http://www.heise.de");

    // pre launch the chrome browser, bind services etc
    warmup();

    urlET = (EditText) findViewById(R.id.urlID);

    // pre load a webpage manually 
    Button prepareBt = (Button) findViewById(R.id.prepareBt);
    assert prepareBt != null;
    prepareBt.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            mayLaunch(null);
        
    );

    //launch webpage manually
    Button launchBt = (Button) findViewById(R.id.launchBt);
    assert launchBt != null;
    launchBt.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            launch(null);
        
    );

    //start a loop that serves webpages every 10 seconds
    Button cycleBt = (Button) findViewById(R.id.cycleBt);
    assert cycleBt != null;
    cycleBt.setOnClickListener(new View.OnClickListener() 
        @Override
        public void onClick(View v) 
            if(cycleThread !=null)
                cycleThread.interrupt();

            cycleThread = new Thread(cycle);
            cycleThread.start();
        
    );


private Runnable cycle = new Runnable() 
    @Override
    public void run() 
        int i = 0;
        mayLaunch(Uri.parse(urlList.get(i)));
        try 
            Thread.sleep(5000);

            while (true)
                try 
                    Log.d(TAG, "launch: "+urlList.get(i));
                    launch(Uri.parse(urlList.get(i)));
                    i++;
                    if(i>=urlList.size())
                        i=0;
                    Thread.sleep(5000);
                    Log.d(TAG, "prepare: "+urlList.get(i));
                    mayLaunch(Uri.parse(urlList.get(i)));
                    Thread.sleep(5000);

                 catch (InterruptedException e) 
                   e.printStackTrace();
                    break;
                
            
         catch (InterruptedException e) 
            e.printStackTrace();
        
    
;


private void mayLaunch(Uri uri)
    if(uri ==null)
        uri =  Uri.parse(urlET.getText().toString());
    CustomTabsSession session = getSession();
    session.mayLaunchUrl(uri, null, null);

private void launch(Uri uri)
    if(uri ==null)
        uri =  Uri.parse(urlET.getText().toString());
    CustomTabsIntent customTabsIntent = new CustomTabsIntent.Builder(getSession())

            .setToolbarColor(ContextCompat.getColor(this, R.color.colorPrimaryDark))
            .setShowTitle(true)
            .setStartAnimations(this, android.R.anim.slide_in_left, android.R.anim.slide_out_right)
            .setExitAnimations(this, android.R.anim.slide_in_left, android.R.anim.slide_out_right)
            .build();

    customTabsIntent.intent.addFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
    customTabsIntent.launchUrl(this,uri);



public CustomTabsSession getSession() 
    if (mClient == null) 
        mCustomTabsSession = null;
     else if (mCustomTabsSession == null) 
        mCustomTabsSession = mClient.newSession(null);
        Log.d(TAG, "getSession: created new session");
    
    return mCustomTabsSession;


private void warmup()
    if (mClient != null) return;
    String packageName = "com.android.chrome";
    if (packageName == null) return;

    mConnection = new CustomTabsServiceConnection() 
        @Override
        public void onCustomTabsServiceConnected(ComponentName componentName, CustomTabsClient customTabsClient) 
            mClient = customTabsClient;
            mClient.warmup(0L);
        

        @Override
        public void onServiceDisconnected(ComponentName name) 
            mClient = null;
            mCustomTabsSession = null;
        
    ;
    CustomTabsClient.bindCustomTabsService(this, packageName, mConnection);



private void coolDown()
    if (mConnection == null) return;
    unbindService(mConnection);
    mClient = null;
    mCustomTabsSession = null;
    mConnection = null;


public void onDestroy() 
    Log.v("MainActivity", "onDestroy");
    super.onDestroy();
    coolDown();

@Override
public void onBackPressed()

谢谢！

【问题讨论】：

【参考方案1】：

CustomTabs 忽略从后台发送的mayLaunchUrl()。这有两个原因：

避免浪费带宽的简单措施（很容易检查来自同一会话的自定义选项卡不是前台，只是还没有这样做）

通过mayLaunchUrl() 加载的页面当前不保留Window.sessionStorage()，这对于App -> CustomTab 转换来说不是问题，但是对于在单个CustomTab 中导航，这可能会打破用户对导航模式的假设，例如：