Java按鈕沒有顯示？

Question

我使用下面的代碼，我有一個沒有顯示的按鈕。 我認為它與“SetContentView”有關，因為如果我刪除其中一個按鈕就會出現。 我不知道如何解決這個問題以便一切都顯示出來？ 謝謝！

import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.net.wifi.WifiConfiguration;
import android.net.wifi.WifiManager;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;

import android.widget.Button;
import android.widget.TextView;

public class TestActivity extends Activity {
/** Called when the activity is first created. 
 * @return */



@Override
public void onCreate(Bundle savedInstanceState) {    
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main);
    Button OffWifi = (Button)findViewById(R.id.offwifi);
    OffWifi.setOnClickListener(new OnClickListener() { 
      public void onClick(View v) {                 
          WifiManager wifiManager = (WifiManager)getBaseContext().getSystemService(Context.WIFI_SERVICE);
            wifiManager.setWifiEnabled(false);          
          }        
      });



    TextView tv = new TextView(this);       
    TextView status = new TextView(this);                  


    WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE); 
    WifiConfiguration wc = new WifiConfiguration();  
    wc.SSID = "\"Test\""; //IMP! This should be in Quotes!! 

    wc.hiddenSSID = true; 
    wc.status = WifiConfiguration.Status.ENABLED;      
    wc.priority = 10; 
    wc.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.WPA_PSK); 
    wc.allowedProtocols.set(WifiConfiguration.Protocol.RSN);  
    wc.allowedProtocols.set(WifiConfiguration.Protocol.WPA); 
    wc.allowedAuthAlgorithms.set(WifiConfiguration.AuthAlgorithm.OPEN); 
    wc.allowedAuthAlgorithms.set(WifiConfiguration.AuthAlgorithm.SHARED); 
    wc.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.CCMP); 
    wc.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.TKIP); 
    wc.preSharedKey = "\"Password\""; 
    WifiManager  wifiManag = (WifiManager) this.getSystemService(WIFI_SERVICE); 
    boolean res1 = wifiManag.setWifiEnabled(true); 
    int res = wifi.addNetwork(checkPreviousConfiguration(wc)); 
    Log.d("WifiPreference", "add Network returned " + res ); 
    boolean es = wifi.saveConfiguration(); 
    Log.d("WifiPreference", "saveConfiguration returned " + es ); 
    boolean b = wifi.enableNetwork(res, true);    
    Log.d("WifiPreference", "enableNetwork returned " + b );   

    tv.setText("You are now connected!  " +
            "Version 1.1");

    status.setText("The was an error connecting, please try again.");

       //@Override

    try {

        Thread.sleep(5000);

         ConnectivityManager connec = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE); 

         if (connec != null && (connec.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTED) ||(connec.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTED)){  
                //You are connected, do something online. 
                setContentView(tv);

            }else if (connec.getNetworkInfo(0).getState() == NetworkInfo.State.DISCONNECTED ||  connec.getNetworkInfo(1).getState() == NetworkInfo.State.DISCONNECTED ) {              
                //Not connected.         
               setContentView(status);
            }  

    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }





}

public WifiConfiguration checkPreviousConfiguration(WifiConfiguration wc) {
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE); 
 List<WifiConfiguration> configs = wifi.getConfiguredNetworks();     
    for(WifiConfiguration config : configs) {         
        if(config.SSID.equals(wc.SSID)) return config;     
        }     
    return wc; 
    } 

}

主XML文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >

<TextView
android:id="@+id/tv"
android:layout_width="246dp"
android:layout_height="wrap_content" />


<Button
android:id="@+id/offwifi"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Turn Wifi Off" />

</LinearLayout>

Answer 1

您開始活動，將其內容視圖設置為至少包含一個按鈕的內容。然后您創建TextViews的新實例。 然后在OnCreate中，將內容視圖設置為其中一個文本視圖。 如果已連接，則視圖將替換為TextView，如果未連接，則視圖將替換為TextView。 如果您刪除了一個額外設置的內容呼叫，您將看到該按鈕取決於您是否已連接。

這種行為可能是您想要的，或者您可能想要做的是將TextView添加到布局中，並使用FindViewById以與按鈕上的句柄相同的方式獲取它們的句柄。 然后，您可以避開try塊中的所有內容，因為textviews已經使用新文本進行了更新。 您的代碼目前所做的是用文本視圖替換整個布局。

Answer 2

你需要在main.xml布局文件中獲取根對象，即

LinearLayout layout = (LinearLayout) findViewById( R.id.linearlayout1 );

然后你可以添加到該布局（它可能沒有被命名為linearlayout1）

layout.addView ( status );

Answer 3

setContentView（）不會向顯示添加視圖，而是替換它們。 這就是你的按鈕消失的原因。

在XML布局中使用現有的tv而不是創建新的tv，並且只調用setContentReview（）一次。

像這樣：

super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button OffWifi = (Button)findViewById(R.id.offwifi);
OffWifi.setOnClickListener(new OnClickListener() { 
  public void onClick(View v) {                 
      WifiManager wifiManager = (WifiManager)getBaseContext().getSystemService(Context.WIFI_SERVICE);
        wifiManager.setWifiEnabled(false);          
      }        
  });


// remove these lines
// TextView tv = new TextView(this);       
// TextView status = new TextView(this);                  

// add this line
TextView tv= (TextView) findViewById(R.id.tv);


WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE); 
WifiConfiguration wc....

 ect.ect. 

Log.d("WifiPreference", "enableNetwork returned " + b );   

// let's do this later
//tv.setText("You are now connected!  " +
//        "Version 1.1");

//status.setText("The was an error connecting, please try again.");

   //@Override

try {

    Thread.sleep(5000);

     ConnectivityManager connec = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE); 

     if (connec != null && (connec.getNetworkInfo(1).getState() == NetworkInfo.State.CONNECTED) ||(connec.getNetworkInfo(0).getState() == NetworkInfo.State.CONNECTED)){  

            //You are connected, do something online. 

            // setting the ContentView replaces everything, so don't do that
            //setContentView(tv);

            tv.setText("You are now connected!  " +
               "Version 1.1");



        }else if (connec.getNetworkInfo(0).getState() == NetworkInfo.State.DISCONNECTED ||  connec.getNetworkInfo(1).getState() == NetworkInfo.State.DISCONNECTED ) {              
            //Not connected.         


           //setContentView(status);
           tv.setText("The was an error connecting, please try again.");
        }  

} catch (InterruptedException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

}