堆棧內存溢出
  簡體   English   中英

每次啟動時Android應用程序崩潰

[英]Android application crashes every time on startup

 原文  2014-07-24 14:39:41  4   4    java/ android/ crash/ startup

問題描述

我開始在Android Studio中編寫我的第一個應用程序，在此階段它應該做的是單擊帶有數字的按鈕，然后將其輸出到文本字段中。 當我運行此代碼時，應用程序在啟動時崩潰，我不知道出了什么問題。

MyActivity.java 

package com.example.david.calculator;

import android.app.Activity;
import android.os.Bundle; 
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

import org.w3c.dom.Text;


public class MyActivity extends Activity {

EditText results;
private int number;
final EditText result = (EditText) findViewById(R.id.number);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_my);
    Button one = (Button) findViewById(R.id.button);
    one.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            BtnPressed(1);
        }
    });

}

private void BtnPressed(int i) {
    result.setText(Integer.toString(i));
}


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

activity_my.xml 

<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=".MyActivity">

<EditText
    android:layout_width="fill_parent"
    android:layout_height="50dp"
    android:id="@+id/number"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:hint="0"
    android:background="#ffe7e7e7"
    android:textSize="30sp"
    android:gravity="center_vertical|right"
    android:paddingRight="20dp"
    android:editable="true"
    android:enabled="true"
    android:numeric="integer|signed|decimal" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="1"
    android:id="@+id/button"
    android:layout_below="@+id/number"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_marginTop="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="2"
    android:id="@+id/button2"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button"
    android:layout_toRightOf="@+id/button"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="3"
    android:id="@+id/button3"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button2"
    android:layout_toRightOf="@+id/button2"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="4"
    android:id="@+id/button4"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_below="@+id/button"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="5"
    android:id="@+id/button5"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button4"
    android:layout_toRightOf="@+id/button4"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="6"
    android:id="@+id/button6"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button5"
    android:layout_toRightOf="@+id/button5"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="7"
    android:id="@+id/button7"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_below="@+id/button4"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="8"
    android:id="@+id/button8"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button7"
    android:layout_toRightOf="@+id/button7"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="9"
    android:id="@+id/button9"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button8"
    android:layout_toRightOf="@+id/button8"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="0"
    android:id="@+id/button11"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_below="@+id/button7"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"
    android:layout_marginTop="10dp" />

<Button
    android:layout_width="160dp"
    android:layout_height="75dp"
    android:text="="
    android:id="@+id/button12"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button11"
    android:layout_toRightOf="@+id/button11"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="+"
    android:id="@+id/button13"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button3"
    android:layout_toRightOf="@+id/button3"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="-"
    android:id="@+id/button14"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button6"
    android:layout_toRightOf="@+id/button6"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="*"
    android:id="@+id/button15"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button9"
    android:layout_toRightOf="@+id/button9"
    android:layout_marginLeft="10dp" />

<Button
    android:layout_width="75dp"
    android:layout_height="75dp"
    android:text="/"
    android:id="@+id/button16"
    android:textSize="50sp"
    android:background="#ff0fdf22"
    android:layout_alignTop="@+id/button12"
    android:layout_toRightOf="@+id/button12"
    android:layout_marginLeft="10dp" />

Logcat： 

07-24 16:30:07.894  26564-26564/com.example.david.calculator D/AndroidRuntime﹕ Shutting down VM
07-24 16:30:07.894  26564-26564/com.example.david.calculator W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x4190aba8)
07-24 16:30:07.899  26564-26564/com.example.david.calculator E/AndroidRuntime﹕ FATAL      EXCEPTION: main
Process: com.example.david.calculator, PID: 26564
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.david.calculator/com.example.david.calculator.MyActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5001)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at android.app.Activity.findViewById(Activity.java:1884)
        at com.example.david.calculator.MyActivity.<init>(MyActivity.java:18)
        at java.lang.Class.newInstanceImpl(Native Method)
        at java.lang.Class.newInstance(Class.java:1208)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2101)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)  
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5001)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
        at dalvik.system.NativeStart.main(Native Method)

非常感謝您的所有答復。

4 個解決方案

解決方案1
 1  2014-07-24 14:42:23

你應該搬家 

final EditText result = (EditText) findViewById(R.id.number);

在setContentView(..)之后的onCreate(...)內部

更正的代碼 

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

EditText result = (EditText) findViewById(R.id.number);

Button one = (Button) findViewById(R.id.button);
one.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        BtnPressed(1);
    }
  });

}

解決方案2
 1 已采納  2014-07-24 14:42:48

您在主類中而不是在類的onCreate方法中設置EditText。 如果尚未創建活動，則找不到視圖。 

public class MyActivity extends Activity {

EditText results;
private int number;
final EditText result = (EditText) findViewById(R.id.number);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_my);
    Button one = (Button) findViewById(R.id.button);
    one.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            BtnPressed(1);
        }
    });

}

應該成為 

public class MyActivity extends Activity {

EditText results;
private int number;
private EditText result;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_my);
    result = (EditText) findViewById(R.id.number);
    Button one = (Button) findViewById(R.id.button);
    one.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            BtnPressed(1);
        }
    });

}

您在日志中收到NullPointerException，這應該可以解決它。

解決方案3
 0  2014-07-24 14:41:19

檢查您的代碼：

最終EditText結果=（EditText）findViewById（R.id.number）;

應該在setContentView（）方法之后，就像按鈕一樣。

解決方案4
 0  2014-07-24 14:41:19

你應該做這個： 

final EditText result = (EditText) findViewById(R.id.number);

在setContentView之后的onCreate中。

暫無
暫無

聲明:本站的技術帖子網頁，遵循CC BY-SA 4.0協議，如果您需要轉載，請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.

相關問題 Android應用程序在啟動時崩潰 我的應用程序在啟動時崩潰 應用程序在啟動時崩潰 Android應用程序啟動后崩潰，沒有任何錯誤 如何使用廣告優化 android 應用程序的啟動時間 Android應用在啟動時崩潰 Eclipse-Android應用在啟動時崩潰？ 簡單的android應用在啟動時崩潰 LibGDX And​​roid應用程序在啟動時崩潰 Android Studio在啟動時突然崩潰
相關標簽
 
粵ICP備18138465號  © 2020-2024 STACKOOM.COM