执行我的应用程序时出现空指针异常,我不知道为什么。问题出现在线路上:
task.execute("");
但我不确定为什么这会返回一个空指针异常。(我已经验证我有互联网连接,并且它连接的 XML 文件是完整的并且可以正常工作。)
资源:
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();
}
}