如何在Android设备上制作一个占据屏幕50%大小的警告对话框?
此示例演示如何在Android设备上制作一个占据屏幕50%大小的警告对话框。
步骤1 − 在Android Studio中创建一个新项目,转到文件 ⇒ 新建项目,并填写所有必需的详细信息以创建新项目。
步骤2 − 将以下代码添加到res/layout/activity_main.xml。
<?xml version="1.0" encoding="utf-8"?> <androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true" android:id="@+id/coordinator_layout" tools:context=".MainActivity"> <Button android:id="@+id/btnAlert" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Show Alert Dialog" android:layout_gravity="top|center_horizontal" tools:ignore="MissingConstraints" /&glt; </androidx.coordinatorlayout.widget.CoordinatorLayout>
步骤3 − 将以下代码添加到src/MainActivity.java
package com.app.sample; import androidx.appcompat.app.AppCompatActivity; import androidx.coordinatorlayout.widget.CoordinatorLayout; import android.app.AlertDialog; import android.os.Bundle; import android.app.Activity; import android.content.Context; import android.util.DisplayMetrics; import android.view.View; import android.view.WindowManager; import android.widget.Button; public class MainActivity extends AppCompatActivity { private Context mContext; private Activity mActivity; private CoordinatorLayout mCLayout; private Button mButton; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mContext = getApplicationContext(); mActivity = MainActivity.this; mCLayout = (CoordinatorLayout) findViewById(R.id.coordinator_layout); mButton = (Button) findViewById(R.id.btn_alert); mButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { AlertDialog.Builder builder = new AlertDialog.Builder(mActivity); builder.setTitle("Say Hello!"); builder.setMessage("Are you want to say it?"); builder.setPositiveButton("Say",null); builder.setNegativeButton("No",null); AlertDialog dialog = builder.create(); dialog.show(); DisplayMetrics displayMetrics = new DisplayMetrics(); getWindowManager().getDefaultDisplay().getMetrics(displayMetrics); int displayWidth = displayMetrics.widthPixels; int displayHeight = displayMetrics.heightPixels; WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(); layoutParams.copyFrom(dialog.getWindow().getAttributes()); int dialogWindowWidth = (int) (displayWidth * 0.5f); int dialogWindowHeight = (int) (displayHeight * 0.5f); layoutParams.width = dialogWindowWidth; layoutParams.height = dialogWindowHeight; dialog.getWindow().setAttributes(layoutParams); } }); } }
步骤4 − 将以下代码添加到Manifests/AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.app.sample"> <application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"> <activity android:name=".MainActivity"> <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
让我们尝试运行您的应用程序。我假设您已将实际的Android移动设备连接到您的计算机。要从Android Studio运行应用程序,请打开项目的其中一个活动文件,然后单击运行 工具栏中的图标。选择您的移动设备作为选项,然后检查您的移动设备,它将显示您的默认屏幕 −
点击 这里 下载项目代码。
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