您好，我正在嘗試讓我在主 XML 檔案中的按鈕僅在沒有互聯網時出現所以這就是為什么我可以讓按鈕僅在沒有互聯網時出現，因此除非有互聯網，否則它不會顯示在其他任何地方有人請幫幫我嗎？
Blow 我已經列出了主要 XML 和主要 Java 檔案的代碼
xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<WebView
android:layout_width="10dp"
android:layout_height="10dp"
tools:ignore="MissingConstraints"
tools:layout_editor_absoluteX="200dp"
tools:layout_editor_absoluteY="361dp"/>
<Button
android:id="@ id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Button"
tools:layout_editor_absoluteX="202dp"
tools:layout_editor_absoluteY="399dp" />
</androidx.constraintlayout.widget.ConstraintLayout>\
爪哇
public class MainActivity extends AppCompatActivity {
@SuppressLint("SetJavaScriptEnabled")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WebView webView = new WebView(this);
WebSettings webSettings = webView.getSettings();
webSettings.setBuiltInZoomControls(true);
webSettings.setJavaScriptEnabled(true);
setContentView(webView);
webView.getSettings().setLoadWithOverviewMode(true);
webView.getSettings().setUseWideViewPort(true);
webView.getSettings().setSupportZoom(true);
webView.getSettings().setBuiltInZoomControls(true);
webView.getSettings().setDisplayZoomControls(false);
webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
webView.setScrollbarFadingEnabled(false);
if(isNetworkAvailable(this)){
webView.loadUrl("https://racks.tk");
} else {
Toast.makeText(this,"No internet. Please check internet connection and try again", Toast.LENGTH_LONG).show();
}
}
public static boolean isNetworkAvailable(Context context) {
ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivityManager != null) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
NetworkCapabilities capabilities = connectivityManager.getNetworkCapabilities(connectivityManager.getActiveNetwork());
return capabilities != null && (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) || capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) || capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET));
} else {
NetworkInfo activeNetwork = connectivityManager.getActiveNetworkInfo();
return activeNetwork != null && activeNetwork.isConnected();
}
}
return false;
}
uj5u.com熱心網友回復：
您正在以編程方式創建 Web 視圖，然后嘗試從 XML 檔案訪問按鈕，并且您沒有在 Java 檔案中鏈接 XML 檔案，因此它崩潰了。使用此代碼完全更新您的代碼
XML 檔案 - activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<ProgressBar
android:id="@ id/my_progress"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:indeterminate="true"/>
<WebView
android:id="@ id/my_webview"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<Button
android:id="@ id/reload_btn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="Retry" />
</RelativeLayout>
java 檔案 - MainActivity.java
import androidx.appcompat.app.AppCompatActivity;
import android.annotation.SuppressLint;
import android.content.Context;
import android.graphics.Bitmap;
import android.net.ConnectivityManager;
import android.net.NetworkCapabilities;
import android.net.NetworkInfo;
import android.os.Build;
import android.os.Bundle;
import android.view.View;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
@SuppressLint("SetJavaScriptEnabled")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
WebView webView = findViewById(R.id.my_webview);
Button reloadBtn = findViewById(R.id.reload_btn);
ProgressBar progress = findViewById(R.id.my_progress);
WebSettings webSettings = webView.getSettings();
webSettings.setBuiltInZoomControls(true);
webSettings.setJavaScriptEnabled(true);
webSettings.setLoadWithOverviewMode(true);
webSettings.setUseWideViewPort(true);
webSettings.setSupportZoom(true);
webSettings.setBuiltInZoomControls(true);
webSettings.setDisplayZoomControls(false);
webView.setScrollBarStyle(WebView.SCROLLBARS_OUTSIDE_OVERLAY);
webView.setScrollbarFadingEnabled(false);
webView.setWebViewClient(new WebViewClient(){
@Override
public void onPageStarted(WebView view, String url, Bitmap favicon) {
super.onPageStarted(view, url, favicon);
webView.setVisibility(View.GONE);
}
@Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
progress.setVisibility(View.GONE);
webView.setVisibility(View.VISIBLE);
}
});
if (isNetworkAvailable(this)) {
webView.loadUrl("https://racks.tk");
reloadBtn.setVisibility(View.GONE);
} else {
Toast.makeText(this, "No internet. Please check internet connection and try again", Toast.LENGTH_LONG).show();
reloadBtn.setVisibility(View.VISIBLE);
}
reloadBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (isNetworkAvailable(MainActivity.this)){
reloadBtn.setVisibility(View.GONE);
webView.loadUrl("https://racks.tk");
}else {
reloadBtn.setVisibility(View.VISIBLE);
Toast.makeText(MainActivity.this, "No internet. Please check internet connection and try again", Toast.LENGTH_LONG).show();
}
}
});
}
public static boolean isNetworkAvailable(Context context) {
ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
if (connectivityManager != null) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
NetworkCapabilities capabilities = connectivityManager.getNetworkCapabilities(connectivityManager.getActiveNetwork());
return capabilities != null && (capabilities.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) || capabilities.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) || capabilities.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET));
} else {
NetworkInfo activeNetwork = connectivityManager.getActiveNetworkInfo();
return activeNetwork != null && activeNetwork.isConnected();
}
}
return false;
}
}
uj5u.com熱心網友回復：
您缺少@Override：
Button button = findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override //Right here
public void onClick(View v) {
webView.loadUrl( "javascript:window.location.reload( true )" );
}
});
uj5u.com熱心網友回復：
按鈕按鈕= findViewById(R.id.button);
if(isNetworkAvailable(this)){
webView.loadUrl("myurl.com");
button.setVisibility(View.VISIBLE)
} else {
button.setVisibility(View.GONE)
Toast.makeText(this,"check internet connection and try again", Toast.LENGTH_LONG).show();
}
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