NullPointerException异常引起的：task.execute（＆QUOT;＆QUOT;）; [英] NullPointerException Caused by: task.execute("");
本文介绍了NullPointerException异常引起的：task.execute（＆QUOT;＆QUOT;）;的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我执行我的应用程序时，得到一个空指针异常，我不知道为什么。上线出现该问题：
task.execute（）;
但我不知道为什么会回来跟一个空指针异常。 （我已经验证我有互联网连接，它是连接是否完好和功能的XML文件。）
来源：
公共类UpdateActivity扩展活动实现OnClickListener {
公共静态INT TotalSteps = 8;
私人TelephonyManager TM;
私人按钮mUpdateButton = NULL;
私人按钮mAssistUpdateButton = NULL;
私人按钮mAssistInstrButton = NULL;
私人TextView的mReadAgainButton = NULL;
私人诠释mInstructionNumber = 0;
AlertDialog mConfirmAlert = NULL;
私人NetworkTask任务;
@覆盖
保护无效的onCreate（包savedInstanceState）{
super.onCreate（savedInstanceState）;
TM =（TelephonyManager）getSystemService（TELEPHONY_SERVICE）;
INT NETWORKTYPE = tm.getNetworkType（）;
INT phoneType = tm.getPhoneType（）;
INT版本= android.os.Build.VERSION.SDK_INT;
如果（phoneType == TelephonyManager.PHONE_TYPE_CDMA
|| （phoneType！= TelephonyManager.PHONE_TYPE_GSM
＆功放;＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_GPRS
＆功放;＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_EDGE
＆功放;＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_HSDPA
＆功放;＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_HSPA
＆功放;＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_HSPAP
＆功放;＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_HSUPA
＆功放;＆安培; NETWORKTYPE = TelephonyManager.NETWORK_TYPE_UMTS和放大器;！＆安培; NETWORKTYPE！= TelephonyManager.NETWORK_TYPE_LTE））{
//如果手机类型为CDMA或
//电话手机类型不是GSM和网络类型是没有
//网络类型在声明中表示
//显示不兼容性消息
showAlert（的getString（R.string.incomp_sm_dialog））;
//网络类型看，因为一些药片没有手机类型。
//我们依靠在这种情况下，网络类型
}否则，如果（！（tm.getSimState（）== TelephonyManager.SIM_STATE_ABSENT
|| （tm.getSimOperator（））
.equals（的getString（R.string.numeric_tmo））|| （TM
.getSimOperator（））。等于（的getString（R.string.numeric_att））））{
//如果SIM卡是present，不是T型钼网SIM卡，
//显示错误信息提示，指示使用SM SIM卡
showAlert（的getString（R.string.insert_sm_dialog））;
} //没有SIM卡或SIM卡与T-莫MNC MCC present
否则，如果（版本＆LT; VERSION_ codeS.ICE_CREAM_SANDWICH）{
比ICS //初始UI安装的版本更低
的setContentView（R.layout.update）;
mUpdateButton =（按钮）findViewById（R.id.update_button）;
mUpdateButton.setOnClickListener（本）;
}其他{// ICS及以上
// task.execute（）;
如果（（tm.getSimOperator（））。等于（的getString（R.string.numeric_tmo））
|| （tm.getSimOperator（））
.equals（的getString（R.string.numeric_att）））{
task.execute（）;
//设备具有T型钼网络的SIM卡MCC和MNC正确
//人口
//减少步骤数，以6
TotalSteps = 6;
}
//
//初始UI设置为ICS及以上
的setContentView（R.layout.assist_update）;
字符串assistUpdate =的getString（R.string.apn_app_text_cta2）;
CharSequence中的StyledText = Html.fromHtml（assistUpdate）;
TextView的assistText =（TextView中）findViewById（R.id.apn_app_text_cta2）;
assistText.setText（的StyledText）;
mAssistUpdateButton =（按钮）findViewById（R.id.assist_update_btn）;
mAssistUpdateButton.setOnClickListener（本）;
}
}
公共无效的onClick（视图v）{
如果（V == mUpdateButton）{
//被选为版本比ICS更低更新按钮
//的setContentView（R.layout.updating）;
onClickMethod（五）;
意图I =新的意图（这一点，ConfigFinalActivity.class）;
startActivity（ⅰ）;
完（）;
}否则，如果（V == mAssistUpdateButton）{
//被选为ICS及以上更新按钮
//获取协助更新UI TextView的
TextView的电视=（TextView中）findViewById（R.id.apn_app_text_cta2）;
字符串文本=;
CharSequence中的StyledText =文本;
开关（mInstructionNumber）{
情况下0：
//获得对应的指令串资源
//第二个指令集
文=的String.Format（的getString（R.string.apn_app_text_instr）
TotalSteps）;
的StyledText = Html.fromHtml（文本）;
//更新与正确的指令集的TextView的
tv.setText（的StyledText）;
所以正确的指令//增量指令号
//串资源可以是检索下一时间的更新
//按钮是pressed
mInstructionNumber ++;
打破;
情况1：
文=的getString（R.string.apn_app_text_instr2）;
的StyledText = Html.fromHtml（文本）;
tv.setText（的StyledText）;
所以正确的指令//增量指令号
//串资源可以是检索下一时间的更新
//按钮是pressed
mInstructionNumber ++;
打破;
案例2：
//决胜盘说明，更改为相应的布局
的setContentView（R.layout.assist_instructions）;
字符串assistUpdateInstr =的String.Format（
的getString（R.string.apn_app_text_instr3），TotalSteps）;
的StyledText = Html.fromHtml（assistUpdateInstr）;
TextView的assistInstrText =（TextView中）findViewById（R.id.updated_text）;
assistInstrText.setText（的StyledText）;
mAssistInstrButton =（按钮）findViewById（R.id.assist_instr_btn）;
mReadAgainButton =（TextView中）findViewById（R.id.read_again_btn）;
mAssistInstrButton.setOnClickListener（本）;
mReadAgainButton.setOnClickListener（本）;
}
}否则，如果（V == mAssistInstrButton）{
//LET'S做到这一点按钮，在最后指示屏幕ICS和
//中选择了
//创建ConfigActivity意向
意图I =新的意图（这一点，ConfigFinalActivity.class）;
//调用ConfigActivity意图，开始协助更新
startActivity（ⅰ）;
完（）;
}否则，如果（V == mReadAgainButton）{
//返回指令1套，如果选择再次读取
mInstructionNumber = 0;
的setContentView（R.layout.assist_update）;
字符串assistUpdate =的getString（R.string.apn_app_text_cta2）;
CharSequence中的StyledText = Html.fromHtml（assistUpdate）;
TextView的assistText =（TextView中）findViewById（R.id.apn_app_text_cta2）;
assistText.setText（的StyledText）;
mAssistUpdateButton =（按钮）findViewById（R.id.assist_update_btn）;
mAssistUpdateButton.setOnClickListener（本）;
}
}
公共无效onClickMethod（视图v）{
mUpdateButton =（按钮）findViewById（R.drawable.btn_update_active_hdpi）;
}
私人无效showAlert（字符串消息）{
AlertDialog.Builder建设者=新AlertDialog.Builder（本）;
builder.setMessage（消息）.setPositiveButton（OK，
新DialogInterface.OnClickListener（）{
公共无效的onClick（DialogInterface对话框，INT ID）{
UpdateActivity.this.finish（）;
}
}）;
mConfirmAlert = builder.create（）;
mConfirmAlert.show（）;
}
}
解决方案
据我所知，你永远不会初始化工作。您在这里声明它
私人NetworkTask任务;
但你需要调用执行前初始化（）。像
任务=新NetworkTask（）; //传递PARAMS构造器，如果需要
task.execute（）;
I'm getting a null pointer exception when executing my app and I'm not sure why. The issue occurs on the line:
task.execute("");
but I'm not sure why this would come back with a null pointer exception. (I've verified I have internet connectivity and the XML file it is connecting to is intact and functional.)
SOURCE:
public class UpdateActivity extends Activity implements OnClickListener {
public static int TotalSteps = 8;
private TelephonyManager tm;
private Button mUpdateButton = null;
private Button mAssistUpdateButton = null;
private Button mAssistInstrButton = null;
private TextView mReadAgainButton = null;
private int mInstructionNumber = 0;
AlertDialog mConfirmAlert = null;
private NetworkTask task;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
tm = (TelephonyManager) getSystemService(TELEPHONY_SERVICE);
int networkType = tm.getNetworkType();
int phoneType = tm.getPhoneType();
int version = android.os.Build.VERSION.SDK_INT;
if (phoneType == TelephonyManager.PHONE_TYPE_CDMA
|| (phoneType != TelephonyManager.PHONE_TYPE_GSM
&& networkType != TelephonyManager.NETWORK_TYPE_GPRS
&& networkType != TelephonyManager.NETWORK_TYPE_EDGE
&& networkType != TelephonyManager.NETWORK_TYPE_HSDPA
&& networkType != TelephonyManager.NETWORK_TYPE_HSPA
&& networkType != TelephonyManager.NETWORK_TYPE_HSPAP
&& networkType != TelephonyManager.NETWORK_TYPE_HSUPA
&& networkType != TelephonyManager.NETWORK_TYPE_UMTS && networkType != TelephonyManager.NETWORK_TYPE_LTE)) {
// If the phone type is CDMA or
// the phone phone type is not GSM and the network type is none of
// the network types indicated in the statement
// Display incompatibility message
showAlert(getString(R.string.incomp_sm_dialog));
// Network type is looked because some tablets have no phone type.
// We rely on network type in such cases
} else if (!(tm.getSimState() == TelephonyManager.SIM_STATE_ABSENT
|| (tm.getSimOperator())
.equals(getString(R.string.numeric_tmo)) || (tm
.getSimOperator()).equals(getString(R.string.numeric_att)))) {
// if SIM is present and is NOT a T-Mo network SIM,
// display Error message alert indicating to use SM SIM
showAlert(getString(R.string.insert_sm_dialog));
}// No SIM or SIM with T-Mo MNC MCC present
else if (version < VERSION_CODES.ICE_CREAM_SANDWICH) {
// Initial UI setup for versions lower than ICS
setContentView(R.layout.update);
mUpdateButton = (Button) findViewById(R.id.update_button);
mUpdateButton.setOnClickListener(this);
} else {// ICS and up
// task.execute();
if ((tm.getSimOperator()).equals(getString(R.string.numeric_tmo))
|| (tm.getSimOperator())
.equals(getString(R.string.numeric_att))) {
task.execute("");
// Device has T-Mo network SIM card MCC and MNC correctly
// populated
// Reduce number of steps to 6
TotalSteps = 6;
}
//
// Initial UI setup for ICS and up
setContentView(R.layout.assist_update);
String assistUpdate = getString(R.string.apn_app_text_cta2);
CharSequence styledText = Html.fromHtml(assistUpdate);
TextView assistText = (TextView) findViewById(R.id.apn_app_text_cta2);
assistText.setText(styledText);
mAssistUpdateButton = (Button) findViewById(R.id.assist_update_btn);
mAssistUpdateButton.setOnClickListener(this);
}
}
public void onClick(View v) {
if (v == mUpdateButton) {
// Update button for versions lower than ICS is selected
// setContentView(R.layout.updating);
onClickMethod(v);
Intent i = new Intent(this, ConfigFinalActivity.class);
startActivity(i);
finish();
} else if (v == mAssistUpdateButton) {
// Update button for ICS and up is selected
// Get the TextView in the Assist Update UI
TextView tv = (TextView) findViewById(R.id.apn_app_text_cta2);
String text = "";
CharSequence styledText = text;
switch (mInstructionNumber) {
case 0:
// Retrieve the instruction string resource corresponding the
// 2nd set of instructions
text = String.format(getString(R.string.apn_app_text_instr),
TotalSteps);
styledText = Html.fromHtml(text);
// Update the TextView with the correct set of instructions
tv.setText(styledText);
// Increment instruction number so the correct instructions
// string resource can be retrieve the next time the update
// button is pressed
mInstructionNumber++;
break;
case 1:
text = getString(R.string.apn_app_text_instr2);
styledText = Html.fromHtml(text);
tv.setText(styledText);
// Increment instruction number so the correct instructions
// string resource can be retrieve the next time the update
// button is pressed
mInstructionNumber++;
break;
case 2:
// Final set of instructions-Change to the corresponding layout
setContentView(R.layout.assist_instructions);
String assistUpdateInstr = String.format(
getString(R.string.apn_app_text_instr3), TotalSteps);
styledText = Html.fromHtml(assistUpdateInstr);
TextView assistInstrText = (TextView) findViewById(R.id.updated_text);
assistInstrText.setText(styledText);
mAssistInstrButton = (Button) findViewById(R.id.assist_instr_btn);
mReadAgainButton = (TextView) findViewById(R.id.read_again_btn);
mAssistInstrButton.setOnClickListener(this);
mReadAgainButton.setOnClickListener(this);
}
} else if (v == mAssistInstrButton) {
// "LET'S DO THIS" Button in final instructions screen for ICS and
// up is selected
// Create ConfigActivity Intent
Intent i = new Intent(this, ConfigFinalActivity.class);
// Invoke ConfigActivity Intent to start the assisted update
startActivity(i);
finish();
} else if (v == mReadAgainButton) {
// go back to 1st set of instructions if read again is selected
mInstructionNumber = 0;
setContentView(R.layout.assist_update);
String assistUpdate = getString(R.string.apn_app_text_cta2);
CharSequence styledText = Html.fromHtml(assistUpdate);
TextView assistText = (TextView) findViewById(R.id.apn_app_text_cta2);
assistText.setText(styledText);
mAssistUpdateButton = (Button) findViewById(R.id.assist_update_btn);
mAssistUpdateButton.setOnClickListener(this);
}
}
public void onClickMethod(View v) {
mUpdateButton = (Button) findViewById(R.drawable.btn_update_active_hdpi);
}
private void showAlert(String message) {
AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage(message).setPositiveButton("OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
UpdateActivity.this.finish();
}
});
mConfirmAlert = builder.create();
mConfirmAlert.show();
}
}
解决方案
As far as I can tell, you never initialize task. You declare it here
private NetworkTask task;
but you need to initialize before calling execute(). Like
task = new NetworkTask(); // pass params to constructor if needed
task.execute();
这篇关于NullPointerException异常引起的：task.execute（＆QUOT;＆QUOT;）;的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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