[問題] 新手求助

[qqaaz (知足常樂)]

如有違板規 煩請提醒
============================

我是剛學習eclipes的新手
安裝完主程式 開啟第一個內建的app
成功輸出apk到手機 可以正常開啟那個hello world的原始app

開始學習第二步
製作button來改變"hello world"文字
完全照教學的步驟輸入程式碼

關鍵內容如下
==========================================================
MyButton=(Button)findViewById(R.id.button1);
tv1=(TextView)findViewById(R.id.textview1);
MyButton.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View v) {
tv1.setText("測試測試");
}}
);
==========================================================

但不管怎麼做 一開啟app就會跳 unfortunately xxx has stopped
以下是錯誤log 但我看不懂.. 請大家幫我看看出了什麼問題

03-24 04:41:22.210: W/dalvikvm(911): threadid=1: thread exiting with uncaught
exception (group=0xb4a89ba8)
03-24 04:41:22.220: E/AndroidRuntime(911): FATAL EXCEPTION: main
03-24 04:41:22.220: E/AndroidRuntime(911): Process: hhhr.ff, PID: 911
03-24 04:41:22.220: E/AndroidRuntime(911): java.lang.RuntimeException: Unable
to start activity ComponentInfo{hhhr.ff/hhhr.ff.MainActivity}:
java.lang.NullPointerException
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.ActivityThread.access$800(ActivityThread.java:135)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.os.Handler.dispatchMessage(Handler.java:102)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.os.Looper.loop(Looper.java:136)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.ActivityThread.main(ActivityThread.java:5017)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
java.lang.reflect.Method.invokeNative(Native Method)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
java.lang.reflect.Method.invoke(Method.java:515)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
dalvik.system.NativeStart.main(Native Method)
03-24 04:41:22.220: E/AndroidRuntime(911): Caused by:
java.lang.NullPointerException
03-24 04:41:22.220: E/AndroidRuntime(911):      at
hhhr.ff.MainActivity.onCreate(MainActivity.java:24)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.Activity.performCreate(Activity.java:5231)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-24 04:41:22.220: E/AndroidRuntime(911):      at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
03-24 04:41:22.220: E/AndroidRuntime(911):      ... 11 more



ps.在eclipes設計畫面中都沒看到其他叉叉的錯誤警告

麻煩各位了 謝謝


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◆ From: 114.36.209.11
→ qqaaz:在猜會不會是AVD設定問題..但也嘗試過好幾種設定都不行
推 cooper6334:Eclipse是IDE,你學的是Android
推 cooper6334:八成是你xml有問題才會findViewById找不到
→ qqaaz:謝謝提示 我研究看看XML設定
→ qqaaz:可以請問怎麼判斷出findViewById找不到的?
推 cooper6334:nullpointerexception
→ qqaaz:謝謝
→ cooper6334:有AndroidDev板，那邊比較適合
→ qqaaz:謝謝你 如果有違板規 非常抱歉
→ cooper6334:其實主要是因為這邊根本沒人XD