Android có một cơ chế sẵn sàng để đóng ứng dụng một cách an toàn theo tài liệu của nó. Trong Hoạt động cuối cùng được thoát (thường là Hoạt động chính xuất hiện đầu tiên khi ứng dụng bắt đầu), chỉ cần đặt một vài dòng trong phương thức onDestroy (). Cuộc gọi đến System.runFinalulatorsOnExit (true) đảm bảo rằng tất cả các đối tượng sẽ được hoàn thành và rác được thu thập khi ứng dụng thoát. Bạn cũng có thể hủy ứng dụng một cách nhanh chóng thông qua android.os.Process.killProcess (android.os.Process.myPid ()) nếu bạn thích. Cách tốt nhất để làm điều này là đặt một phương thức như sau trong một lớp trợ giúp và sau đó gọi nó bất cứ khi nào ứng dụng cần phải bị giết. Ví dụ: trong phương thức hủy của hoạt động gốc (giả sử rằng ứng dụng không bao giờ giết chết hoạt động này):
Ngoài ra, Android sẽ không thông báo cho ứng dụng về sự kiện phím HOME , do đó bạn không thể đóng ứng dụng khi nhấn phím HOME . Android bảo lưu sự kiện khóa HOME cho chính nó để nhà phát triển không thể ngăn người dùng rời khỏi ứng dụng của họ. Tuy nhiên, bạn có thể xác định bằng phím HOME được nhấn bằng cách đặt cờ thành đúng trong lớp người trợ giúp giả sử rằng phím HOME đã được nhấn, sau đó thay đổi cờ thành sai khi xảy ra sự kiện cho thấy phím HOME không được nhấn và sau đó kiểm tra xem phím HOME được nhấn trong phương thức onStop () của hoạt động.
Đừng quên xử lý phím HOME cho bất kỳ menu nào và trong các hoạt động được bắt đầu bởi các menu. Cũng vậy với khóa TÌM KIẾM . Dưới đây là một số lớp ví dụ để minh họa:
Đây là một ví dụ về hoạt động gốc giết chết ứng dụng khi nó bị hủy:
package android.example;
/**
* @author Danny Remington - MacroSolve
*/
public class HomeKey extends CustomActivity {
public void onDestroy() {
super.onDestroy();
/*
* Kill application when the root activity is killed.
*/
UIHelper.killApp(true);
}
}
Đây là một hoạt động trừu tượng có thể được mở rộng để xử lý khóa HOME cho tất cả các hoạt động mở rộng nó:
package android.example;
/**
* @author Danny Remington - MacroSolve
*/
import android.app.Activity;
import android.view.Menu;
import android.view.MenuInflater;
/**
* Activity that includes custom behavior shared across the application. For
* example, bringing up a menu with the settings icon when the menu button is
* pressed by the user and then starting the settings activity when the user
* clicks on the settings icon.
*/
public abstract class CustomActivity extends Activity {
public void onStart() {
super.onStart();
/*
* Check if the app was just launched. If the app was just launched then
* assume that the HOME key will be pressed next unless a navigation
* event by the user or the app occurs. Otherwise the user or the app
* navigated to this activity so the HOME key was not pressed.
*/
UIHelper.checkJustLaunced();
}
public void finish() {
/*
* This can only invoked by the user or the app finishing the activity
* by navigating from the activity so the HOME key was not pressed.
*/
UIHelper.homeKeyPressed = false;
super.finish();
}
public void onStop() {
super.onStop();
/*
* Check if the HOME key was pressed. If the HOME key was pressed then
* the app will be killed. Otherwise the user or the app is navigating
* away from this activity so assume that the HOME key will be pressed
* next unless a navigation event by the user or the app occurs.
*/
UIHelper.checkHomeKeyPressed(true);
}
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.settings_menu, menu);
/*
* Assume that the HOME key will be pressed next unless a navigation
* event by the user or the app occurs.
*/
UIHelper.homeKeyPressed = true;
return true;
}
public boolean onSearchRequested() {
/*
* Disable the SEARCH key.
*/
return false;
}
}
Dưới đây là ví dụ về màn hình menu xử lý phím HOME :
/**
* @author Danny Remington - MacroSolve
*/
package android.example;
import android.os.Bundle;
import android.preference.PreferenceActivity;
/**
* PreferenceActivity for the settings screen.
*
* @see PreferenceActivity
*
*/
public class SettingsScreen extends PreferenceActivity {
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
addPreferencesFromResource(R.layout.settings_screen);
}
public void onStart() {
super.onStart();
/*
* This can only invoked by the user or the app starting the activity by
* navigating to the activity so the HOME key was not pressed.
*/
UIHelper.homeKeyPressed = false;
}
public void finish() {
/*
* This can only invoked by the user or the app finishing the activity
* by navigating from the activity so the HOME key was not pressed.
*/
UIHelper.homeKeyPressed = false;
super.finish();
}
public void onStop() {
super.onStop();
/*
* Check if the HOME key was pressed. If the HOME key was pressed then
* the app will be killed either safely or quickly. Otherwise the user
* or the app is navigating away from the activity so assume that the
* HOME key will be pressed next unless a navigation event by the user
* or the app occurs.
*/
UIHelper.checkHomeKeyPressed(true);
}
public boolean onSearchRequested() {
/*
* Disable the SEARCH key.
*/
return false;
}
}
Dưới đây là ví dụ về lớp trình trợ giúp xử lý khóa HOME trên ứng dụng:
package android.example;
/**
* @author Danny Remington - MacroSolve
*
*/
/**
* Helper class to help handling of UI.
*/
public class UIHelper {
public static boolean homeKeyPressed;
private static boolean justLaunched = true;
/**
* Check if the app was just launched. If the app was just launched then
* assume that the HOME key will be pressed next unless a navigation event
* by the user or the app occurs. Otherwise the user or the app navigated to
* the activity so the HOME key was not pressed.
*/
public static void checkJustLaunced() {
if (justLaunched) {
homeKeyPressed = true;
justLaunched = false;
} else {
homeKeyPressed = false;
}
}
/**
* Check if the HOME key was pressed. If the HOME key was pressed then the
* app will be killed either safely or quickly. Otherwise the user or the
* app is navigating away from the activity so assume that the HOME key will
* be pressed next unless a navigation event by the user or the app occurs.
*
* @param killSafely
* Primitive boolean which indicates whether the app should be
* killed safely or quickly when the HOME key is pressed.
*
* @see {@link UIHelper.killApp}
*/
public static void checkHomeKeyPressed(boolean killSafely) {
if (homeKeyPressed) {
killApp(true);
} else {
homeKeyPressed = true;
}
}
/**
* Kill the app either safely or quickly. The app is killed safely by
* killing the virtual machine that the app runs in after finalizing all
* {@link Object}s created by the app. The app is killed quickly by abruptly
* killing the process that the virtual machine that runs the app runs in
* without finalizing all {@link Object}s created by the app. Whether the
* app is killed safely or quickly the app will be completely created as a
* new app in a new virtual machine running in a new process if the user
* starts the app again.
*
* <P>
* <B>NOTE:</B> The app will not be killed until all of its threads have
* closed if it is killed safely.
* </P>
*
* <P>
* <B>NOTE:</B> All threads running under the process will be abruptly
* killed when the app is killed quickly. This can lead to various issues
* related to threading. For example, if one of those threads was making
* multiple related changes to the database, then it may have committed some
* of those changes but not all of those changes when it was abruptly
* killed.
* </P>
*
* @param killSafely
* Primitive boolean which indicates whether the app should be
* killed safely or quickly. If true then the app will be killed
* safely. Otherwise it will be killed quickly.
*/
public static void killApp(boolean killSafely) {
if (killSafely) {
/*
* Notify the system to finalize and collect all objects of the app
* on exit so that the virtual machine running the app can be killed
* by the system without causing issues. NOTE: If this is set to
* true then the virtual machine will not be killed until all of its
* threads have closed.
*/
System.runFinalizersOnExit(true);
/*
* Force the system to close the app down completely instead of
* retaining it in the background. The virtual machine that runs the
* app will be killed. The app will be completely created as a new
* app in a new virtual machine running in a new process if the user
* starts the app again.
*/
System.exit(0);
} else {
/*
* Alternatively the process that runs the virtual machine could be
* abruptly killed. This is the quickest way to remove the app from
* the device but it could cause problems since resources will not
* be finalized first. For example, all threads running under the
* process will be abruptly killed when the process is abruptly
* killed. If one of those threads was making multiple related
* changes to the database, then it may have committed some of those
* changes but not all of those changes when it was abruptly killed.
*/
android.os.Process.killProcess(android.os.Process.myPid());
}
}
}