**I am developing a remote app, which has lots of buttons in my Activity. i choose three different onclickListeners and onCheckedChangeListener. I am getting a nullpointer exception on first statement when i try to setOnClickListener class to buttons. Need Help..!**
public void OnCreate(){
if ((getResources().getConfiguration().screenLayout == Configuration.SCREENLAYOUT_SIZE_LARGE) && screenDpi==1)
{
// yes, we are large and set orientation to landscape
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
setContentView(R.layout.tabletlayout7main);
screenLayout = 1;
} else if ((getResources().getConfiguration().screenLayout == Configuration.SCREENLAYOUT_SIZE_LARGE) && screenDpi==1)
{
// yes, we are xlarge and set orientation to landscape
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
setContentView(R.layout.tabletlayout10main);
screenLayout = 1;
} else if (screenDpi==0) {
// no, we are not / less than large and with less pixels(860)
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
setContentView(R.layout.activity_maini);
TextView TviewHome = (TextView) findViewById(R.id.TextViewHome);
//TviewHome.setMinHeight(45);
TviewHome.getLayoutParams().height = 50;
TviewHome.setTextSize((float) 38.0);
}
// Buttons block
//Initialize all the views
terminal = (Button) findViewById(R.id.dthButtonLock);
//Channels And Volume buttons for TV tab here
tvchP = (Button)findViewById(R.id.tvChlPButton);
tvchM = (Button)findViewById(R.id.tvChM);
tvvolP = (Button)findViewById(R.id.tvVPButton);
tvvolM = (Button)findViewById(R.id.tvVolM);
//Directions TV
tvOk = (Button)findViewById(R.id.tvOkButton);
tvDown = (Button)findViewById(R.id.tvDownbutton1);
tvLeft = (Button)findViewById(R.id.tvleftButton);
tvRight = (Button)findViewById(R.id.tvRightButton);
tvUp = (Button)findViewById(R.id.tvUpButton);
// TV MISC Buttons here
tvaV = (Button)findViewById(R.id.tvAVButton);
tvsleep = (Button)findViewById(R.id.tvSleepbutton);
tvpicAdj = (Button)findViewById(R.id.tvPICbutton6);
tvEQ = (Button)findViewById(R.id.tvEQZRbutton10);
tvAsp= (Button)findViewById(R.id.tvASPbutton8);
tvMenu = (Button)findViewById(R.id.tvMenrButton);
tvsndAdj = (Button)findViewById(R.id.tvSNDbutton7);
tvMute = (Button)findViewById(R.id.tvMutButton);
tvReturn = (Button)findViewById(R.id.buttonDoubleBack);
tvZoom = (Button)findViewById(R.id.tvZoombutton9);
//Advanced Controls of TV
atvFf = (Button)findViewById(R.id.tvFFbutton2);
atvFr = (Button)findViewById(R.id.tvFRbutton4);
atvNext = (Button)findViewById(R.id.tvNxtbutton5);
atvPlay = (Button)findViewById(R.id.tvPlaybutton1);
atvPause = (Button)findViewById(R.id.tvPausebutton);
atvPrev = (Button)findViewById(R.id.tvbuttonPrev);
atvStop = (Button)findViewById(R.id.tvStopbutton3);
dvdEject = (Button)findViewById(R.id.dvdEjectbutton);
//Toggle Button Setup for DVD
tvTg = (ToggleButton) findViewById(R.id.tvToggle);
dthTg = (ToggleButton) findViewById(R.id.dthToggle);
dvdTg = (ToggleButton) findViewById(R.id.dvdToggle);
// DTH Controls...
dth1 = (Button)findViewById(R.id.dthOneButton);
dth2 = (Button)findViewById(R.id.dthTwoButton);
dth3 = (Button)findViewById(R.id.dthThrButton);
dth4 = (Button)findViewById(R.id.dthFourButton);
dth5 = (Button)findViewById(R.id.dthFiveButton);
dth6 = (Button)findViewById(R.id.dthSixButton);
dth7 = (Button)findViewById(R.id.dthSevenButton);
dth8 = (Button)findViewById(R.id.dthEightButton);
dth9 = (Button)findViewById(R.id.dthNineButton);
dth0 = (Button)findViewById(R.id.dthZeroButton);
dthMenu = (Button)findViewById(R.id.dthMenubutton);
dthswap = (Button)findViewById(R.id.dthSwapButton);
dthMute = (Button)findViewById(R.id.dthbuttonMute);
dthvolP = (Button)findViewById(R.id.dthViolPButton);
dthvolM = (Button)findViewById(R.id.dthVolMinusButton);
dthchP = (Button)findViewById(R.id.dthChPlusButton);
dthchM = (Button)findViewById(R.id.dthChMinusButton);
dthBlue = (Button)findViewById(R.id.dthButBlue);
dthRed = (Button)findViewById(R.id.dthButRed);
dthGreen = (Button)findViewById(R.id.dthButGreen);
dthYellow = (Button)findViewById(R.id.dthButYellow);
dthGuide = (Button)findViewById(R.id.dthbuttonGuide);
dthFav = (Button)findViewById(R.id.dthbuttonFav);
dthUp = (Button)findViewById(R.id.dthUpButton);
dthDown = (Button)findViewById(R.id.dthDownButton);
dthLeft = (Button)findViewById(R.id.dthLButton);
dthRight = (Button)findViewById(R.id.dthRButton);
dthOk = (Button)findViewById(R.id.dthCButton);
//Listeners Block
//TV Listeners(Total set of 27) Set One
tvchP.setOnClickListener(BTCClickListenerOne);
tvchM.setOnClickListener(BTCClickListenerOne);
tvvolP.setOnClickListener(BTCClickListenerOne);
tvvolM.setOnClickListener(BTCClickListenerOne);
tvOk.setOnClickListener(BTCClickListenerOne);
tvDown.setOnClickListener(BTCClickListenerOne);
tvLeft.setOnClickListener(BTCClickListenerOne);
tvRight.setOnClickListener(BTCClickListenerOne);
tvUp.setOnClickListener(BTCClickListenerOne);
tvaV.setOnClickListener(BTCClickListenerOne);
tvMenu.setOnClickListener(BTCClickListenerOne);
// TV ADVCD SET TWO
tvMute.setOnClickListener(BTCClickListenerOne);
tvsleep.setOnClickListener(BTCClickListenerOne);
tvpicAdj.setOnClickListener(BTCClickListenerOne);
tvsndAdj.setOnClickListener(BTCClickListenerOne);
tvEQ.setOnClickListener(BTCClickListenerOne);
tvAsp.setOnClickListener(BTCClickListenerOne);
tvReturn.setOnClickListener(BTCClickListenerOne);
tvZoom.setOnClickListener(BTCClickListenerOne);
// DTH OnClickListeners(total set of 30)...........
dth1.setOnClickListener(BTCClickListenerTwo);
dth2.setOnClickListener(BTCClickListenerTwo);
dth3.setOnClickListener(BTCClickListenerTwo);
dth4.setOnClickListener(BTCClickListenerTwo);
dth5.setOnClickListener(BTCClickListenerTwo);
dth6.setOnClickListener(BTCClickListenerTwo);
dth7.setOnClickListener(BTCClickListenerTwo);
dth8.setOnClickListener(BTCClickListenerTwo);
dth9.setOnClickListener(BTCClickListenerTwo);
dth0.setOnClickListener(BTCClickListenerTwo);
dthMenu.setOnClickListener(BTCClickListenerTwo);
dthMute.setOnClickListener(BTCClickListenerTwo);
dthswap.setOnClickListener(BTCClickListenerTwo);
dthvolM.setOnClickListener(BTCClickListenerTwo);
dthvolP.setOnClickListener(BTCClickListenerTwo);
dthchM.setOnClickListener(BTCClickListenerTwo);
dthchP.setOnClickListener(BTCClickListenerTwo);
dthUp.setOnClickListener(BTCClickListenerTwo);
dthDown.setOnClickListener(BTCClickListenerTwo);
dthOk.setOnClickListener(BTCClickListenerTwo);
dthLeft.setOnClickListener(BTCClickListenerTwo);
dthRight.setOnClickListener(BTCClickListenerTwo);
dthRed.setOnClickListener(BTCClickListenerTwo);
dthBlue.setOnClickListener(BTCClickListenerTwo);
dthGuide.setOnClickListener(BTCClickListenerTwo);
dthGreen.setOnClickListener(BTCClickListenerTwo);
dthYellow.setOnClickListener(BTCClickListenerTwo);
dthFav.setOnClickListener(BTCClickListenerTwo);
//Advanced Controls of TV
atvFf.setOnClickListener(AdTvListener);
atvFr.setOnClickListener(AdTvListener);
atvNext.setOnClickListener(AdTvListener);
atvPlay.setOnClickListener(AdTvListener);
atvPause.setOnClickListener(AdTvListener);
atvPrev.setOnClickListener(AdTvListener);
atvStop.setOnClickListener(AdTvListener);
dvdEject.setOnClickListener(AdTvListener);
//
tvTg.setOnCheckedChangeListener(OnOffCheckToggle);
dvdTg.setOnCheckedChangeListener(OnOffCheckToggle);
dthTg.setOnCheckedChangeListener(OnOffCheckToggle);
}
然后我在我的应用程序中有四种类型的按钮的监听器类
// OnClickListener Interface for TV Button Controls
public OnClickListener BTCClickListenerOne = new OnClickListener() {
//未实现的方法在这里.. }
//OnClickListener Interface for DTH Button Controls
public OnClickListener BTCClickListenerTwo = new OnClickListener() {
//未实现的方法在这里.. }
// Creating a Seperate OnClickListener for Advanced TV Button Controls
public OnClickListener AdTvListener = new OnClickListener() {
//未实现的metod在这里.. }
// Creating a seperate OnCheckedChange Listener for three toggle buttons
public OnCheckedChangeListener OnOffCheckToggle = new OnCheckedChangeListener(){
//未实现的metod在这里.. }
答案 0 :(得分：2)
您在onCreate：
super.onCreate(savedInstanceState);
setContentView(R.layout.<main layout>);
将它放在开头。显然，如果您在提出问题时粘贴了所有内容，则表示您缺少设置内容视图。
答案 1 :(得分：1)
首先设置内容视图。
setContentViewR.layout.yourxml);
然后只有Activity会识别视图和它所在的xml。否则它将通过NullPointer异常。