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為什么使用TextView更新int值並顯示它給我崩潰了？

[英]Why is using TextView to update int value and display it giving me a crash?

 原文  2013-04-21 11:10:12  4   3    java/ android/ android-layout/ dynamic/ textview

問題描述

我正在嘗試為Android開發文字冒險。 已經找到了一種無需創建新活動即可更改“頁面”的微妙方法。

現在，我試圖在每個布局中包含永久的int值，這些值在更改時會立即更新。

即黃金/健康價值。 根據玩家在游戲中的選擇，它將：-將布局更改為相應的頁面-更改int值為Gold +10，健康-1

我在mainactivity類中開發了以下代碼： 

package com.example.textadventure;

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

public class MainActivity extends Activity {

    private int int1 = 1;

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

    public void changelayout1(View view){
        setContentView(R.layout.activity_main2);
        int1 += 1;
    }
    public void changelayout2(View view){
        setContentView(R.layout.activity_main);
        int1 += 1;
    }
    public void changelayout3(View view){
        setContentView(R.layout.activity_main3);
        int1 += 1;
    }



    public void onResume() {
        super.onResume();
        TextView textView = (TextView) this.findViewById(R.id.mytextview1);
        textView.setText(String.valueOf(int1));
    }



}

結果如下：

我的LogCat 

04-19 16:09:57.446: E/Trace(3204): error opening trace file: No such file or directory (2)
04-19 16:09:59.016: D/AndroidRuntime(3204): Shutting down VM
04-19 16:09:59.016: W/dalvikvm(3204): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
04-19 16:09:59.036: E/AndroidRuntime(3204): FATAL EXCEPTION: main
04-19 16:09:59.036: E/AndroidRuntime(3204): java.lang.RuntimeException: Unable to resume activity {com.example.textadventure/com.example.textadventure.MainActivity}: java.lang.NullPointerException
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2742)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2771)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2235)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.os.Looper.loop(Looper.java:137)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread.main(ActivityThread.java:5041)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at java.lang.reflect.Method.invokeNative(Native Method)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at java.lang.reflect.Method.invoke(Method.java:511)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at dalvik.system.NativeStart.main(Native Method)
04-19 16:09:59.036: E/AndroidRuntime(3204): Caused by: java.lang.NullPointerException
04-19 16:09:59.036: E/AndroidRuntime(3204):     at com.example.textadventure.MainActivity.onResume(MainActivity.java:28)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1185)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.Activity.performResume(Activity.java:5182)
04-19 16:09:59.036: E/AndroidRuntime(3204):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2732)
04-19 16:09:59.036: E/AndroidRuntime(3204):     ... 12 more
04-19 16:10:02.386: I/Process(3204): Sending signal. PID: 3204 SIG: 9
04-19 16:15:42.576: D/AndroidRuntime(3292): Shutting down VM
04-19 16:15:42.586: W/dalvikvm(3292): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
04-19 16:15:42.596: E/AndroidRuntime(3292): FATAL EXCEPTION: main
04-19 16:15:42.596: E/AndroidRuntime(3292): java.lang.RuntimeException: Unable to resume activity {com.example.textadventure/com.example.textadventure.MainActivity}: java.lang.NullPointerException
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2742)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2771)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2235)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.os.Looper.loop(Looper.java:137)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread.main(ActivityThread.java:5041)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at java.lang.reflect.Method.invokeNative(Native Method)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at java.lang.reflect.Method.invoke(Method.java:511)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at dalvik.system.NativeStart.main(Native Method)
04-19 16:15:42.596: E/AndroidRuntime(3292): Caused by: java.lang.NullPointerException
04-19 16:15:42.596: E/AndroidRuntime(3292):     at com.example.textadventure.MainActivity.onResume(MainActivity.java:31)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1185)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.Activity.performResume(Activity.java:5182)
04-19 16:15:42.596: E/AndroidRuntime(3292):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2732)
04-19 16:15:42.596: E/AndroidRuntime(3292):     ... 12 more
04-19 16:18:00.358: E/Trace(3350): error opening trace file: No such file or directory (2)
04-19 16:18:01.796: D/AndroidRuntime(3350): Shutting down VM
04-19 16:18:01.810: W/dalvikvm(3350): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
04-19 16:18:01.866: E/AndroidRuntime(3350): FATAL EXCEPTION: main
04-19 16:18:01.866: E/AndroidRuntime(3350): java.lang.RuntimeException: Unable to resume activity {com.example.textadventure/com.example.textadventure.MainActivity}: java.lang.NullPointerException
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2742)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2771)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2235)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.os.Looper.loop(Looper.java:137)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread.main(ActivityThread.java:5041)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at java.lang.reflect.Method.invokeNative(Native Method)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at java.lang.reflect.Method.invoke(Method.java:511)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at dalvik.system.NativeStart.main(Native Method)
04-19 16:18:01.866: E/AndroidRuntime(3350): Caused by: java.lang.NullPointerException
04-19 16:18:01.866: E/AndroidRuntime(3350):     at com.example.textadventure.MainActivity.onResume(MainActivity.java:31)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1185)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.Activity.performResume(Activity.java:5182)
04-19 16:18:01.866: E/AndroidRuntime(3350):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2732)
04-19 16:18:01.866: E/AndroidRuntime(3350):     ... 12 more
04-19 16:22:06.477: E/Trace(3412): error opening trace file: No such file or directory (2)
04-19 16:22:08.086: D/AndroidRuntime(3412): Shutting down VM
04-19 16:22:08.116: W/dalvikvm(3412): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
04-19 16:22:08.207: E/AndroidRuntime(3412): FATAL EXCEPTION: main
04-19 16:22:08.207: E/AndroidRuntime(3412): java.lang.RuntimeException: Unable to resume activity {com.example.textadventure/com.example.textadventure.MainActivity}: java.lang.NullPointerException
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2742)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2771)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2235)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.os.Looper.loop(Looper.java:137)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread.main(ActivityThread.java:5041)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at java.lang.reflect.Method.invokeNative(Native Method)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at java.lang.reflect.Method.invoke(Method.java:511)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at dalvik.system.NativeStart.main(Native Method)
04-19 16:22:08.207: E/AndroidRuntime(3412): Caused by: java.lang.NullPointerException
04-19 16:22:08.207: E/AndroidRuntime(3412):     at com.example.textadventure.MainActivity.onResume(MainActivity.java:35)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1185)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.Activity.performResume(Activity.java:5182)
04-19 16:22:08.207: E/AndroidRuntime(3412):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2732)
04-19 16:22:08.207: E/AndroidRuntime(3412):     ... 12 more
04-19 16:22:10.786: I/Process(3412): Sending signal. PID: 3412 SIG: 9
04-19 16:25:22.020: D/AndroidRuntime(3477): Shutting down VM
04-19 16:25:22.020: W/dalvikvm(3477): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
04-19 16:25:22.026: E/AndroidRuntime(3477): FATAL EXCEPTION: main
04-19 16:25:22.026: E/AndroidRuntime(3477): java.lang.RuntimeException: Unable to resume activity {com.example.textadventure/com.example.textadventure.MainActivity}: java.lang.NullPointerException
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2742)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2771)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2235)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.os.Looper.loop(Looper.java:137)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread.main(ActivityThread.java:5041)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at java.lang.reflect.Method.invokeNative(Native Method)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at java.lang.reflect.Method.invoke(Method.java:511)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at dalvik.system.NativeStart.main(Native Method)
04-19 16:25:22.026: E/AndroidRuntime(3477): Caused by: java.lang.NullPointerException
04-19 16:25:22.026: E/AndroidRuntime(3477):     at com.example.textadventure.MainActivity.onResume(MainActivity.java:36)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1185)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.Activity.performResume(Activity.java:5182)
04-19 16:25:22.026: E/AndroidRuntime(3477):     at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2732)
04-19 16:25:22.026: E/AndroidRuntime(3477):     ... 12 more

正如我說的，我想要這樣的東西：

http://postimg.org/image/dy7g2ts6v/

我已經知道如何制作按鈕來切換布局，但是我不能在不崩潰的情況下顯示整數。 :(

3 個解決方案

解決方案1
 0 已采納  2013-04-21 11:14:06

似乎並非所有布局都具有mytextview1視圖。 確保每個布局XML中都存在這樣的視圖。

考慮使用兩個片段，一個片段顯示永久信息，另一個片段根據需要在布局之間切換。

片段指南：

http://developer.android.com/training/basics/fragments/index.html

http://developer.android.com/guide/components/fragments.html

解決方案2
 0  2013-04-21 11:28:24

TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    tv= (TextView) findViewById(R.id.tv);
    //textview with id should be defined in activity_main.xml 
    //set text to textview.
}

確保您在activity_main中具有文本視圖。 由於您已經使用activity_main設置了布局，因此需要確保您在activity_main中具有textview

http://developer.android.com/training/basics/activity-lifecycle/starting.html

您必須實現onCreate（）方法以執行基本的應用程序啟動邏輯，該邏輯在活動的整個生命周期中僅應發生一次 。 您可以在oncreate中初始化textiew。

假設活動暫停並恢復onReusme（）的調用，那么每當您需要查找textview的ID時，就可以了。 因此，在oncreate中初始化textiew。

最好開始新活動或使用片段，而不是在同一屏幕上設置不同的布局。

activity_main 

<LinearLayout 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:orientation="vertical"
tools:context=".DisplayMessageActivity" >

<TextView
android:id="@+id/tv"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
</LinearLayout>

解決方案3
 0  2013-04-21 12:04:42

像這樣做： 

private Integer int1 = 1;

及以下 

TextView textView = (TextView) findViewById(R.id.mytextview1);
textView.setText(int1.toString());

注意，您不需要this.findViewById，只需直接使用findViewById。

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