下午好。我开始学习androidstudio,并决定创建一个应用程序“trafficlight”。它应该每2秒改变一次颜色,当颜色改变时,开始按钮应该在停止按钮上改变。这就是问题所在。我看了视频,写了类似的代码,但什么也没发生:(。如果对您来说不难,请检查我的代码并给我建议如何改进:)。这是我的密码:
主要活动的xml:
<?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"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#FFFFFF"
tools:context=".MainActivity" >
<LinearLayout
android:id="@+id/Balb1"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_marginTop="108dp"
android:background="@color/Grey"
android:orientation="horizontal"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.498"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
</LinearLayout>
<LinearLayout
android:id="@+id/Balb2"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_marginTop="16dp"
android:background="#ACA5A5"
android:orientation="horizontal"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/Balb3"></LinearLayout>
<LinearLayout
android:id="@+id/Balb3"
android:layout_width="100dp"
android:layout_height="100dp"
android:layout_marginTop="16dp"
android:background="#ACA5A5"
android:orientation="horizontal"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/Balb1">
</LinearLayout>
<Button
android:id="@+id/startButton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginTop="40dp"
android:text="Start"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/Balb2" />
</androidx.constraintlayout.widget.ConstraintLayout>
代码如下:
package com.example.myapplication;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
public class MainActivity extends AppCompatActivity implements onClick {
private LinearLayout B1, B2, B3;
private Button button1;
private boolean startOrStop = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
B1 = findViewById(R.id.Balb1);
B2 = findViewById(R.id.Balb2);
B3 = findViewById(R.id.Balb3);
button1 = findViewById(R.id.startButton);
}
public void onClickStart(View view){
if(!startOrStop) {
button1.setText(getString(R.string.stop));
startOrStop = true;
new Thread((Runnable) () -> {
while (startOrStop){
try {
Thread.sleep(2000);
} catch (InterruptedException e){
e.printStackTrace();
}
}
}).start();
}
else {
startOrStop = false;
button1.setText(getString(R.string.start));
}
}
@Override
protected void onDestroy() {
super.onDestroy();
startOrStop = false;
}
}
1条答案
按热度按时间dgiusagp1#
问题出现在以下代码中:
while是无限运行的,因为在循环中没有使startorstop变量为false的逻辑。它还会阻塞ui线程。
所以应该编写一些逻辑,使startorstop变量在循环中为false。否则你不需要任何while循环,这里没有什么简单的东西,写了下面的代码就可以了。