Android——Intent.addflags的使用

本文详细介绍了Android中Activity的四种启动模式:standard、singleTop、singleTask及singleInstance,并解释了如何通过Intent Flags来实现特定的启动行为。

activity的启动模式:4种

在manifest里面对应的activity中增加android:launchMode=""属性指定启动模式

和在activity中增加

Intent intent2=new Intent();
intent2.setClass(MainActivity2.this, MainActivity3.class);
intent2.addFlags(Intent. FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent2);


1、standard:默认模式:每次启动都会创建一个新的activity对象,放到目标任务栈中

2、singleTop:判断当前的任务栈顶是否存在相同的activity对象,如果存在,则直接使用,如果不存在,那么创建新的activity对象放入栈中

3、singleTask:在任务栈中会判断是否存在相同的activity,如果存在,那么会清除该activity之上的其他activity对象显示,如果不存在,则会创建一个新的activity放入栈顶

4、singleIntance:会在一个新的任务栈中创建activity,并且该任务栈种只允许存在一个activity实例,其他调用该activity的组件会直接使用该任务栈种的activity对象


intent flags属性来指定启动模式:Intent.FLAG_ACTIVITY_NEW_TASK      相当于singleTask

Intent. FLAG_ACTIVITY_CLEAR_TOP相当于singleTop


我的MainActivity如下:package com.example.bus; import android.Manifest; import android.content.Intent; import android.content.pm.PackageManager; import android.net.Uri; import android.os.Build; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.Window; import android.view.WindowManager; import android.widget.Toast; import androidx.annotation.NonNull; import androidx.appcompat.app.AlertDialog; import androidx.appcompat.app.AppCompatActivity; import androidx.core.app.ActivityCompat; import androidx.core.content.ContextCompat; import androidx.navigation.NavController; import androidx.navigation.Navigation; import androidx.navigation.ui.AppBarConfiguration; import androidx.navigation.ui.NavigationUI; import com.example.bus.databinding.ActivityMainBinding; import com.google.android.material.bottomnavigation.BottomNavigationView; public class MainActivity extends AppCompatActivity { private ActivityMainBinding binding; private static final String SAVED_NAV_ID = "saved_nav_id"; private static final int LOCATION_PERMISSION_REQUEST_CODE = 1001; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); // ✅ 添加日志:查看冷启动时权限是否已被系统撤销 Log.d("PERMISSION_DEBUG", "onCreate: FINE_LOCATION_GRANTED = " + (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED)); binding = ActivityMainBinding.inflate(getLayoutInflater()); setContentView(binding.getRoot()); // 👉 在这里插入:设置状态栏 setStatusBar(); BottomNavigationView navView = findViewById(R.id.nav_view); AppBarConfiguration appBarConfiguration = new AppBarConfiguration.Builder( R.id.navigation_home, R.id.navigation_map, R.id.navigation_settings) .build(); NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_activity_main); NavigationUI.setupActionBarWithNavController(this, navController, appBarConfiguration); NavigationUI.setupWithNavController(navView, navController); // 更新底部导航逻辑 navView.setOnItemSelectedListener(item -> { int itemId = item.getItemId(); if (itemId == R.id.navigation_map) { ensureFineLocationPermission(() -> { if (navController.getCurrentDestination().getId() != R.id.navigation_map) { navController.navigate(R.id.navigation_map); } }); return true; } navController.navigate(itemId); return true; }); // 恢复上次选中的底部菜单项 if (savedInstanceState != null) { int savedId = savedInstanceState.getInt(SAVED_NAV_ID, R.id.navigation_home); navView.setSelectedItemId(savedId); } } /** * 🔑 强制设置状态栏为深色背景 + 白色图标 * 解决 MIUI、EMUI、ColorOS 等系统自动启用浅色状态栏的问题 */ private void setStatusBar() { Window window = getWindow(); // 设置状态栏背景颜色 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) { window.addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS); window.clearFlags(WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS); window.setStatusBarColor(ContextCompat.getColor(this, R.color.purple_700)); // 使用主题定义的颜色 } // 关键:移除 LIGHT_STATUS_BAR 标志 → 图标变为白色 if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) { View decorView = window.getDecorView(); int flags = decorView.getSystemUiVisibility(); flags &= ~View.SYSTEM_UI_FLAG_LIGHT_STATUS_BAR; // 清除浅色状态栏标志 decorView.setSystemUiVisibility(flags); } } // 通用权限保障方法(所有进地图前都必须走这里) public void ensureFineLocationPermission(Runnable onGranted) { boolean hasFine = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED; if (hasFine) { onGranted.run(); // 权限存在,直接执行 } else { requestFineLocationPermission(onGranted); // 否则发起请求 } } /** * 请求精确定位权限(带解释说明) */ private void requestFineLocationPermission(Runnable onGranted) { boolean hasFine = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED; if (hasFine) { onGranted.run(); return; } if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.ACCESS_FINE_LOCATION)) { new AlertDialog.Builder(this) .setTitle("需要精确定位权限") .setMessage("为了准确查找您附近的公交站点和车辆位置,本应用需要获取您的精确位置。\n否则将无法使用地图相关功能。\n\n请务必选择【允许】或【仅限这一次】。") .setPositiveButton("去允许", (d, w) -> requestFineLocation()) .setNegativeButton("取消", null) .show(); } else { requestFineLocation(); } } private void requestFineLocation() { ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_FINE_LOCATION}, LOCATION_PERMISSION_REQUEST_CODE); } @Override public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) { super.onRequestPermissionsResult(requestCode, permissions, grantResults); if (requestCode == LOCATION_PERMISSION_REQUEST_CODE) { boolean hasFine = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED; if (hasFine) { Toast.makeText(this, "已获得精确定位权限", Toast.LENGTH_SHORT).show(); navigateToMapIfNeeded(); } else { boolean hasCoarse = ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) == PackageManager.PERMISSION_GRANTED; if (hasCoarse) { new AlertDialog.Builder(this) .setTitle("需要精确位置") .setMessage("检测到您使用的是【大致位置】,这会导致地图功能无法正常使用。\n\n" + "请在设置中将定位权限修改为【精确位置】。") .setPositiveButton("去设置", (d, w) -> openAppSettings()) .setNegativeButton("取消", null) .show(); } else { Toast.makeText(this, "定位权限未授予,无法使用地图功能", Toast.LENGTH_LONG).show(); } } } } private void navigateToMapIfNeeded() { NavController navController = Navigation.findNavController(this, R.id.nav_host_fragment_activity_main); if (navController.getCurrentDestination().getId() != R.id.navigation_map) { navController.navigate(R.id.navigation_map); } } private void openAppSettings() { Intent intent = new Intent(android.provider.Settings.ACTION_APPLICATION_DETAILS_SETTINGS); intent.setData(Uri.parse("package:" + getPackageName())); startActivity(intent); } @Override protected void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); BottomNavigationView navView = findViewById(R.id.nav_view); outState.putInt(SAVED_NAV_ID, navView.getSelectedItemId()); } } 我的activity_main.xml如下:<?xml version="1.0" encoding="utf-8"?> <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:id="@+id/container" android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true"> <!-- 替代原来的 paddingTop --> <!--透明 Toolbar 占位--> <androidx.appcompat.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" app:layout_constraintTop_toTopOf="parent" android:visibility="gone" /> <com.google.android.material.bottomnavigation.BottomNavigationView android:id="@+id/nav_view" android:layout_width="0dp" android:layout_height="wrap_content" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintLeft_toLeftOf="parent" app:layout_constraintRight_toRightOf="parent" app:menu="@menu/bottom_nav_menu" /> <fragment android:id="@+id/nav_host_fragment_activity_main" android:name="androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="0dp" app:defaultNavHost="true" app:layout_constraintBottom_toTopOf="@id/nav_view" app:layout_constraintTop_toTopOf="parent" app:navGraph="@navigation/mobile_navigation" /> </androidx.constraintlayout.widget.ConstraintLayout>请问怎么修改
最新发布
10-16
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