我有一个在游戏活动中使用倒数计时器的应用程序。当按下后退按钮时，主要活动加载，但计时器不会停止。当时间在背景上结束时，回合活动结束将加载；即使主活动运行。所以我想提供计时器，当按下后退按钮时停止。我该怎么办？
package com.example.tabuilengilizcenigelitir;
import androidx.appcompat.app.AppCompatActivity;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.os.Bundle;
import android.os.CountDownTimer;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class GameActivity extends AppCompatActivity {
public final static String TEAM_ONE_SCORE = "TEAM_ONE_SCORE";
public final static String TEAM_TWO_SCORE = "TEAM_TWO_SCORE";
public final static String TURN = "TURN";
static private int team1Score;
static private int team2Score;
private int passNum,passNumCopy ;
private int raundNum;
private int raundTime;
private int currentRound;
private int size;
private int language;
private int timeLeft;
private boolean turn ;
boolean startTurn;
CountDownTimer countDownTimer;
ProgressBar mProgressBar;
TextView time,teamName,guessWord,translateWord,tabuWord1,tabuWord2,tabuWord3,scoreText;
ArrayList <Words> words;
Button passButton,tabuButton,trueButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_gamenew3);
mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
mProgressBar.getProgressDrawable().setColorFilter(
Color.RED, android.graphics.PorterDuff.Mode.SRC_IN);
words= new ArrayList<Words>();
teamName = (TextView) findViewById(R.id.teamName);
scoreText=(TextView) findViewById(R.id.score);
startTurn = true;
turn = true ;
teamNameText(turn);
SharedPreferences sharedPref = this.getSharedPreferences("MyData",MODE_PRIVATE);
raundNum = sharedPref.getInt("roundNum",10);
raundTime = sharedPref.getInt("roundTime",60);
passNum = sharedPref.getInt("pasHakki",3);
language = sharedPref.getInt("language",1);
passNumCopy = passNum;
currentRound =1;
timeLeft=raundTime;
team1Score=0;
team2Score=0;
updateRoundNum();
updateScores();
time=(TextView) findViewById(R.id.timeText);
startRoundTimer(false,raundTime);
try {
getCards(language);
} catch (IOException e) {
e.printStackTrace();
}
updateCards();
updateScores();
passButton = (Button) findViewById(R.id.passButton);
tabuButton = (Button) findViewById(R.id.tabuButton);
trueButton = (Button) findViewById(R.id.trueButton);
assert passButton != null;
assert trueButton != null;
assert tabuButton != null;
passButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(passNum>0){
updateCards();
}
passNum--;
updatePas();
}
});
tabuButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(turn){
team1Score--;
}
else{
team2Score--;
}
updateCards();
updateScores();
}
});
trueButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if(turn)
team1Score++;
else
team2Score++;
updateCards();
updateScores();
}
});
}
public int getTeam1Score(){
int _team1Score = this.team1Score;
return _team1Score;
}
public int getTeam2Score(){
int _team2Score = this.team2Score;
return _team2Score;
}
public void updateRoundNum(){
TextView roundText = (TextView) findViewById(R.id.roundText);
roundText.setText("Round:" + currentRound + "/" + raundNum);
currentRound++;
}
public void updateScores(){
if(turn){
scoreText.setText(""+team1Score);
}
else{
scoreText.setText(""+team2Score);
}
}
public void teamNameText(boolean t){
if(t) {
teamName.setText("Team 1");
} else
teamName.setText("Team 2");
}
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1) {
if (resultCode == Activity.RESULT_CANCELED) {
updateScores();
updateCards();
}
}
if (requestCode == 2) {
if (resultCode == Activity.RESULT_CANCELED) {
startTurn = true;
startRoundTimer(true,raundTime);
updateScores();
updateCards();
}
}
}
public void startRoundTimer(boolean started,int _raundTime){
int mills;
if (!started)
mills = _raundTime*1000+1000;
else
mills = _raundTime*1000+1000;
mProgressBar.setMax(_raundTime);
countDownTimer= new CountDownTimer(mills,1000) {
@Override
public void onTick(long l) {
time.setText(String.valueOf(l/1000));
int progress = (int) (l/1000);
mProgressBar.setProgress(progress);
timeLeft=(int) l/1000;
}
@Override
public void onFinish() {
if(!turn) {
if(raundNum+1 == currentRound) {
Intent intent = new Intent(GameActivity.this, EndOfGameActivity.class);
startActivity(intent);
}
updateRoundNum();
}
countDownTimer.cancel();
passNum = passNumCopy;
turn =!turn;
startTurn= false;
timeLeft = raundTime;
passButton.setAlpha((float)1.0);
Intent i = new Intent(GameActivity.this, EndOfRoundActivity.class);
i.putExtra(TEAM_ONE_SCORE, team1Score);
i.putExtra(TEAM_TWO_SCORE, team2Score);
i.putExtra(TURN, turn);
startActivityForResult(i,2);
if (startTurn) {
startRoundTimer(true,raundTime);
}
teamNameText(turn);
}
}.start();
}
public void getCards(int choice) throws IOException {
InputStream input;
BufferedReader file;
switch (choice){
case 1:{
input = this.getResources().openRawResource(R.raw.cards_tr);
file = new BufferedReader(new InputStreamReader(input));
break;
}
case 2:{
input = this.getResources().openRawResource(R.raw.cards_es);
file = new BufferedReader(new InputStreamReader(input));
break;
}
case 3:{
input = this.getResources().openRawResource(R.raw.cards_ger);
file = new BufferedReader(new InputStreamReader(input));
break;
}
default:
throw new IllegalStateException("Unexpected value: " + choice);
}
while(file.ready()){
words.add(new Words(file.readLine(),file.readLine(),file.readLine(),file.readLine(),file.readLine()));
file.readLine();
}
input.close();
file.close();
}
public void updateCards(){
guessWord= (TextView) findViewById(R.id.guessWord);
translateWord =(TextView) findViewById(R.id.translateWord);
tabuWord1= (TextView) findViewById(R.id.tabuWord1);
tabuWord2= (TextView) findViewById(R.id.tabuWord2);
tabuWord3= (TextView) findViewById(R.id.tabuWord3);
size= words.size();
int random = (int)(Math.random()*size);
guessWord.setText(""+words.get(random).guessWord);
translateWord.setText("("+words.get(random).translate+")");
tabuWord1.setText(""+words.get(random).tabuWord1);
tabuWord2.setText(""+words.get(random).tabuWord2);
tabuWord3.setText(""+words.get(random).tabuWord3);
}
protected void onPause() {
super.onPause();
countDownTimer.cancel();
//stop your timer here...
}
protected void onResume() {
super.onResume();
startRoundTimer(true,timeLeft);
}
public void onBackPressed(){
super.onBackPressed();
countDownTimer.cancel();
}
public void updatePas(){
if(passNum==0){
passButton.setAlpha((float) 0.5);
}
}
}
class Words {
String translate,guessWord,tabuWord1,tabuWord2,tabuWord3;
public Words (String w1,String w2,String w3,String w4,String w5){
translate=w1;
guessWord=w2;
tabuWord1=w3;
tabuWord2=w4;
tabuWord3=w5;
}
}
使用此代码来管理您的计时器。在活动或片段的onPause方法中，发送false取消它。
public void startTimer(long time, boolean start) {
if (start) {
timer = new CountDownTimer(time, 1000) {
public void onTick(long millisUntilFinished) {
}
public void onFinish() {
}
}.start();
} else if (timer != null) {
timer.cancel();
}
}
因为在onResume（）方法中再次激活了计时器。实际上在这里：
protected void onResume() {
super.onResume();
startRoundTimer(true,timeLeft);
}
如果您在此处不再启动计时器，它将不会在后台运行。并再次检查这部分代码：
if (!started)
mills = _raundTime*1000+1000;
else
mills = _raundTime*1000+1000;
这两个条件都具有相同的结果。您可以删除这些条件。