Question

我有一些我在Android Studio中工作的代码。我们的目标是创建一个具有计数器的应用程序，当您按下开始按钮时，计数器会快速上升，一旦达到所需的输入，您按下一个停止按钮，它会记录您与所需值的距离。它是测试反应时间等的。问题是每当我在手机或模拟器上运行应用程序时，应用程序会立即崩溃并发出错误＆＃34;不幸的是，定时器测试已停止工作。＆＃34;有谁知道问题可能是什么？

MainActivity.java中的代码：

package com.ultraman11.timertest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {

    public int numCounter = 0;
    public boolean counting = false;

    TextView counter = (TextView) findViewById(R.id.counter);
    TextView difference = (TextView) findViewById(R.id.diff);
    EditText numInput = (EditText) findViewById(R.id.numInput);

    public int userInt = Integer.parseInt(numInput.getText().toString());
    public int differenceInt = Math.abs(numCounter - userInt);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void resetButton(View v){
        numCounter = 0;
        difference.setText("Difference: ");
        counter.setText(Integer.toString(0));
    }

    public void startButton(View v){
        counting = true;
        while(counting){
            numCounter++;
        }
    }

    public void stopButton(View v){
        counting = false;
        difference.setText("Difference: " + Integer.toString(differenceInt));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

activity_main.xml中的代码

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Reset"
        android:id="@+id/button"
        android:nestedScrollingEnabled="false"
        android:onClick="resetButton"
        android:layout_below="@+id/numInput"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="38dp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Start"
        android:id="@+id/button2"
        android:onClick="startButton"
        android:layout_below="@+id/numInput"
        android:layout_alignLeft="@+id/button"
        android:layout_alignStart="@+id/button"
        android:layout_marginTop="112dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="0"
        android:id="@+id/counter"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="79dp" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/numInput"
        android:inputType="number"
        android:layout_below="@+id/counter"
        android:layout_alignLeft="@+id/button"
        android:layout_alignStart="@+id/button"
        android:layout_marginTop="31dp"
        android:layout_alignRight="@+id/button"
        android:layout_alignEnd="@+id/button" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Stop"
        android:id="@+id/button3"
        android:layout_marginTop="23dp"
        android:layout_below="@+id/button2"
        android:layout_alignLeft="@+id/button2"
        android:layout_alignStart="@+id/button2"
        android:onClick="stopButton" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Difference: "
        android:id="@+id/diff"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="43dp" />
</RelativeLayout>

Logcat错误

09-10 17:33:45.103: D/AndroidRuntime(3445): Shutting down VM
09-10 17:33:45.104: E/AndroidRuntime(3445): FATAL EXCEPTION: main
09-10 17:33:45.104: E/AndroidRuntime(3445): Process: com.ultraman11.timertest, PID: 3445
09-10 17:33:45.104: E/AndroidRuntime(3445): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ultraman11.timertest/com.ultraman11.timertest.MainActivity}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.ActivityThread.access$800(ActivityThread.java:151)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.os.Handler.dispatchMessage(Handler.java:102)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.os.Looper.loop(Looper.java:135)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.ActivityThread.main(ActivityThread.java:5254)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at java.lang.reflect.Method.invoke(Native Method)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at java.lang.reflect.Method.invoke(Method.java:372)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
09-10 17:33:45.104: E/AndroidRuntime(3445): Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.support.v7.app.AppCompatDelegateImplBase.onCreate(AppCompatDelegateImplBase.java:124)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.support.v7.app.AppCompatDelegateImplV7.onCreate(AppCompatDelegateImplV7.java:146)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.support.v7.app.AppCompatActivity.onCreate(AppCompatActivity.java:59)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at com.ultraman11.timertest.MainActivity.onCreate(MainActivity.java:26)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.Activity.performCreate(Activity.java:5990)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
09-10 17:33:45.104: E/AndroidRuntime(3445):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
09-10 17:33:45.104: E/AndroidRuntime(3445):     ... 10 more
09-10 17:33:47.163: I/Process(3445): Sending signal. PID: 3445 SIG: 9

Answer 1

当你点击开始时，你立即进入循环，因为计数是真的所以它只是将numCounter增加到infty。

，而不是使用像AsyncTask这样的东西包围增量的东西

编辑：抱歉，我没有明确表示它会立即崩溃，请确保在调用onCreate之前在onCreate方法中初始化你的内容... setContentView（）

Answer 2

在调用findViewById()之前，您无法使用onCreate()。你需要改变：

TextView counter;
TextView difference;
EditText numInput;

并将其设置为onCreate()：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    counter = (TextView) findViewById(R.id.counter);
    difference = (TextView) findViewById(R.id.diff);
    numInput = (EditText) findViewById(R.id.numInput);
}

Answer 3

您必须在 onCreate（） 活动方法中初始化您的观点。我已编辑您的java文件。试试这个。

package com.ultraman11.timertest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.EditText;

public class MainActivity extends AppCompatActivity {

    public int numCounter = 0;
    public boolean counting = false;

    TextView counter;
    TextView difference;
    EditText numInput;

    public int userInt
    public int differenceInt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        counter = (TextView) findViewById(R.id.counter);
        difference = (TextView) findViewById(R.id.diff);
        numInput = (EditText) findViewById(R.id.numInput);

        try{
          userInt = Integer.parseInt(numInput.getText().toString());
        }Catch(Exception e){
          userInt = 0;
        }            
        differenceInt = Math.abs(numCounter - userInt);
    }

    public void resetButton(View v){
        numCounter = 0;
        difference.setText("Difference: ");
        counter.setText(Integer.toString(0));
    }

    public void startButton(View v){
        counting = true;
        while(counting){
            numCounter++;
        }
    }

    public void stopButton(View v){
        counting = false;
        difference.setText("Difference: " + Integer.toString(differenceInt));
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

更新代码

package com.ultraman11.timertest;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {

    public int numCounter = 0;
    public boolean counting = false;

    TextView counter;
    TextView difference;
    EditText numInput;

    public int userInt;
    public int differenceInt;

    TimerTask timertask = null;
    Timer timer = null ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        counter = (TextView) findViewById(R.id.counter);
        difference = (TextView) findViewById(R.id.diff);
        numInput = (EditText) findViewById(R.id.numInput);
    }

    public void resetButton(View v){
        numCounter = 0;
        difference.setText("Difference: ");
        counter.setText(Integer.toString(0));
        if(timertask!=null){
            timertask.cancel();
            timertask = null;
        }
        if(timer!=null){
            timer.cancel();
            timer = null;
        }
    }

    public void startButton(View v){
        if(timertask!=null){
            timertask.cancel();
            timertask = null;
        }
        if(timer!=null){
            timer.cancel();
            timer = null;
        }

        timer = new Timer();
        timertask = new TimerTask() {

            @Override
            public void run() {
                numCounter++;
                runOnUiThread(new Runnable() {
                    public void run() {
                        counter.setText(Integer.toString(numCounter));
                    }
                });
            }
        };
        timer.scheduleAtFixedRate(timertask, 0, 1000);
    }

    public void stopButton(View v){
        if(timertask!=null){
            timertask.cancel();
            timertask = null;
        }
        if(timer!=null){
            timer.cancel();
            timer = null;
        }

        try{
              userInt = Integer.parseInt(numInput.getText().toString());
        }catch(Exception e){
          userInt = 0;
        }            
        differenceInt = Math.abs(numCounter - userInt);
        difference.setText("Difference: " + Integer.toString(differenceInt));
    }

    @Override
    protected void onDestroy() {
        if(timertask!=null){
            timertask.cancel();
            timertask = null;
        }

        if(timer!=null){
            timer.cancel();
            timer = null;
        }
        super.onDestroy();
    }
}

Answer 4

这是一个很多人所犯的简单错误。查看LogCat，它会告诉您需要使用Theme.AppCompat或类似的东西。 AppCompat需要AppCompat。它与设备主题不兼容。您所要做的就是打开AndroidManifest.xml并执行以下操作：

<application
    ...
    android:theme="@style/AppTheme">
    ...
</application>

在/res/values/styles.xml中添加：

<?xml version="1.0" encoding="utf-8"?>
<resources>  
    <style name="AppBaseTheme" parent="Theme.AppCompat"/>
    <style name="AppTheme" parent="AppBaseTheme">
        <!-- Put any customizations here. -->
    </style>
</resources>

Android Studio代码不起作用？

4 个答案: