我是编码新手，目前是一名学生。我正在尝试创建一个简单的计时器应用程序。当我在模拟器中运行计时器应用程序时，它会打开一秒钟，然后强制停止。
我努力了：
1.清洁项目
2.添加android：hasCode =“ true”;
3.下载AppCompat
这是我的MainActivity代码：
package com.example.timer2;
import android.os.Bundle;
import com.google.android.material.floatingactionbutton.FloatingActionButton;
import com.google.android.material.snackbar.Snackbar;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import android.os.CountDownTimer;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
private TextView countdownText;
private Button countdownButton;
private CountDownTimer countDownTimer;
private long timeLeftInMilliseconds = 600000; //10 mins
private boolean timerRunning;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
countdownText = findViewById(R.id.countdown_text);
countdownButton = findViewById(R.id.countdown_button);
countdownButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
startStop();
}
});
}
public void startStop () {
if (timerRunning) {
stopTimer ();
} else {
startTimer ();
}
}
public void startTimer () {
countDownTimer = new CountDownTimer(timeLeftInMilliseconds, 1000) {
@Override
public void onTick(long l) {
timeLeftInMilliseconds = l;
updateTimer ();
}
@Override
public void onFinish() {
}
}.start();
countdownButton.setText("PAUSE");
timerRunning = true;
}
public void stopTimer () {
countDownTimer.cancel();
countdownButton.setText("START");
timerRunning = false;
}
public void updateTimer () {
int minutes = (int) timeLeftInMilliseconds / 600000;
int seconds = (int) timeLeftInMilliseconds % 600000 / 1000;
String timeLeftText;
timeLeftText = "" + minutes;
timeLeftText += ":";
if (seconds < 10) timeLeftText += "0";
timeLeftText += seconds;
countdownText.setText(timeLeftText);
}
}
这是我的清单文件：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.timer2">
<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"
android:hasCode="true">
<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@style/AppTheme.NoActionBar">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
这是我的布局：
<RelativeLayout 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"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".MainActivity"
tools:showIn="@layout/activity_main">
<TextView
android:id="@+id/countdown_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:text="10:00"
android:textSize="50sp"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true"/>
<com.google.android.material.button.MaterialButton
android:id="@+id/countdown_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_centerInParent="true"
android:layout_centerVertical="true"
android:layout_marginBottom="237dp"
android:text="@string/start" />
</RelativeLayout>
这是错误消息：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.timer2, PID: 2947
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.timer2/com.example.timer2.MainActivity}: android.view.InflateException: Binary XML file line #23 in com.example.timer2:layout/activity_main: Binary XML file line #20 in com.example.timer2:layout/content_main: Error inflating class com.google.android.material.button.MaterialButton
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3268)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3407)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7343)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:933)
Caused by: android.view.InflateException: Binary XML file line #23 in com.example.timer2:layout/activity_main: Binary XML file line #20 in com.example.timer2:layout/content_main: Error inflating class com.google.android.material.button.MaterialButton
Caused by: android.view.InflateException: Binary XML file line #20 in com.example.timer2:layout/content_main: Error inflating class com.google.android.material.button.MaterialButton
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Constructor.newInstance0(Native Method)
at java.lang.reflect.Constructor.newInstance(Constructor.java:343)
at android.view.LayoutInflater.createView(LayoutInflater.java:854)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1006)
at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:961)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1123)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1084)
at android.view.LayoutInflater.parseInclude(LayoutInflater.java:1263)
at android.view.LayoutInflater.rInflate(LayoutInflater.java:1119)
at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1084)
at android.view.LayoutInflater.inflate(LayoutInflater.java:682)
at android.view.LayoutInflater.inflate(LayoutInflater.java:534)
at android.view.LayoutInflater.inflate(LayoutInflater.java:481)
at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:545)
at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:161)
at com.example.timer2.MainActivity.onCreate(MainActivity.java:31)
at android.app.Activity.performCreate(Activity.java:7802)
at android.app.Activity.performCreate(Activity.java:7791)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1299)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3243)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3407)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:214)
at android.app.ActivityThread.main(ActivityThread.java:7343)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:933)
Caused by: java.lang.IllegalArgumentException: This component requires that you specify a valid TextAppearance attribute. Update your app theme to inherit from Theme.MaterialComponents (or a descendant).
at com.google.android.material.internal.ThemeEnforcement.checkTextAppearance(ThemeEnforcement.java:170)
at com.google.android.material.internal.ThemeEnforcement.obtainStyledAttributes(ThemeEnforcement.java:75)
at com.google.android.material.button.MaterialButton.<init>(MaterialButton.java:140)
at com.google.android.material.button.MaterialButton.<init>(MaterialButton.java:133)
... 31 more
在此先感谢您的帮助。
最佳答案
tl; dr
将您的应用程序主题更改为从Theme.MaterialComponents或Bridge主题继承。另请注意，您的活动在AndroidManifest.xml中设置了自己的主题设置。
欢迎来到StackOverflow！根据错误消息，您在布局中使用的MaterialButton需要一个继承自Theme.MaterialComponents的应用程序主题。您的应用程序很可能使用默认的AppCompat主题。要纠正该错误，请转到您的src/main/res/values/styles.xml文件，并将主题更改为MaterialComponents主题。例如：
<style name="AppTheme" parent="Theme.MaterialComponents.Light">
<!-- ... -->
</style>
您可以从以下主题中进行选择：
Theme.MaterialComponentsTheme.MaterialComponents.NoActionBarTheme.MaterialComponents.LightTheme.MaterialComponents.Light.NoActionBarTheme.MaterialComponents.Light.DarkActionBarTheme.MaterialComponents.DayNightTheme.MaterialComponents.DayNight.NoActionBarTheme.MaterialComponents.DayNight.DarkActionBar如果必须使用
AppCompat主题（例如，为了与Lollipop下的API级别兼容），则可以从Bridge主题继承。Bridge主题继承自AppCompat主题，但也定义了新主题
为您提供“材料组件”主题属性。
提供了以下Bridge主题：
Theme.MaterialComponents.BridgeTheme.MaterialComponents.Light.BridgeTheme.MaterialComponents.NoActionBar.BridgeTheme.MaterialComponents.Light.NoActionBar.BridgeTheme.MaterialComponents.Light.DarkActionBar.BridgeYou can find more information regarding the Material Themes here.
请注意，您的活动在
AndroidManifest.xml中设置了自己的主题设置：<activity
...
android:theme="@style/AppTheme.NoActionBar">
...
</activity>
这意味着，如果您将
styles.xml中的主题设置为继承自Theme.MaterialComponents.Light.NoActionBar，则您的活动现在将查找名为Theme.MaterialComponents.Light.NoActionBar.NoActionBar的主题，该主题不存在。您可以删除此行，也可以使您的应用继承自Theme.MaterialComponents.Light。关于java - 在模拟器中打开时，应用保持关闭状态，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/57235084/