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嗨每當我嘗試運行這個應用程序，我收到它已停止的錯誤消息。在LogCat上，我在OnCreate方法和行中的「setUpImage（）」行上得到一個空指針異常。 「relativeLayout.addView（電話）」。我現在只是使用圖像考拉和海蜇作爲佔位者，所以不要擔心這些。只是應用程序啓動，圖像不顯示在屏幕上。然後，該應用程序只是與該消息崩潰。我知道這是愚蠢的東西，但它會是非常好的，如果你能幫我......她是我的主要活動不幸的是（android應用程序）已停止。空指針異常
package com.example.togglesilentmode;
import android.graphics.Point;
import android.media.AudioManager;
import android.os.Bundle;
import android.app.Activity;
import android.view.Display;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.RelativeLayout.LayoutParams;
public class MainActivity extends Activity {
int displayWidth, displayHeight;
RelativeLayout relativeLayout;
boolean mPhoneIsSilent=true;
private AudioManager mAudioManager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mAudioManager = (AudioManager)getSystemService(AUDIO_SERVICE);
checkIfPhoneIsSilent();
setUpImage();
relativeLayout = (RelativeLayout)findViewById(R.id.relativeLayout);
}
//SETTING UP THE IMAGE
private void setUpImage(){
Display display = getWindowManager().getDefaultDisplay();
Point size = new Point();
display.getSize(size);
displayWidth = size.x;
displayHeight = size.y;
LayoutParams params = new LayoutParams(LayoutParams.WRAP_CONTENT,
LayoutParams.WRAP_CONTENT);
params.leftMargin = displayWidth/4;
params.topMargin = displayHeight/4;
ImageView phone = new ImageView(this);
phone.setOnClickListener(myOnClickLister);
phone.setLayoutParams(params);
if (mPhoneIsSilent) phone.setImageResource(R.drawable.jellyfish);
else phone.setImageResource(R.drawable.koala);
relativeLayout.addView(phone); <----- NULL POINTER EXCEPTION
}
//IMAGE ON CLICK LISTENER
OnClickListener myOnClickLister = new OnClickListener() {
@Override
public void onClick(View v) {
if(mPhoneIsSilent) {
mAudioManager.setRingerMode(AudioManager.RINGER_MODE_NORMAL);
mPhoneIsSilent = false;
}else {
mAudioManager.setRingerMode(AudioManager.RINGER_MODE_SILENT);
mPhoneIsSilent = true;
}
setUpImage();
}
};
//CHECK IF PHONE IS SILENT
private void checkIfPhoneIsSilent(){
int ringerMode = mAudioManager.getRingerMode();
if (ringerMode == mAudioManager.RINGER_MODE_SILENT) mPhoneIsSilent = true;
else mPhoneIsSilent = false;
}
//ON RESUME METHOD
@Override
protected void onResume(){
super.onResume();
checkIfPhoneIsSilent();
setUpImage();
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
And here is my activity_main.xml file.
<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:id="@+id/relativeLayout"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
</RelativeLayout>