我有两种方法来更新和删除应用程序中的数据，我已在 switch 语句中实现了 try catch，但现在收到以下错误:
01-14 20:38:58.778: D/AndroidRuntime(273): Shutting down VM
01-14 20:38:58.778: W/dalvikvm(273): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
01-14 20:38:58.798: E/AndroidRuntime(273): FATAL EXCEPTION: main
01-14 20:38:58.798: E/AndroidRuntime(273): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.flybase2/com.example.flybase2.viewEdit}: java.lang.NullPointerException
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2585)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.ActivityThread.access$2300(ActivityThread.java:125)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.os.Handler.dispatchMessage(Handler.java:99)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.os.Looper.loop(Looper.java:123)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.ActivityThread.main(ActivityThread.java:4627)
01-14 20:38:58.798: E/AndroidRuntime(273): at java.lang.reflect.Method.invokeNative(Native Method)
01-14 20:38:58.798: E/AndroidRuntime(273): at java.lang.reflect.Method.invoke(Method.java:521)
01-14 20:38:58.798: E/AndroidRuntime(273): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
01-14 20:38:58.798: E/AndroidRuntime(273): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
01-14 20:38:58.798: E/AndroidRuntime(273): at dalvik.system.NativeStart.main(Native Method)
01-14 20:38:58.798: E/AndroidRuntime(273): Caused by: java.lang.NullPointerException
01-14 20:38:58.798: E/AndroidRuntime(273): at com.example.flybase2.viewEdit.<init>(viewEdit.java:63)
01-14 20:38:58.798: E/AndroidRuntime(273): at java.lang.Class.newInstanceImpl(Native Method)
01-14 20:38:58.798: E/AndroidRuntime(273): at java.lang.Class.newInstance(Class.java:1429)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
01-14 20:38:58.798: E/AndroidRuntime(273): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2577)
01-14 20:38:58.798: E/AndroidRuntime(273): ... 11 more
有人能看到这个问题吗？它在没有 try catch 的情况下完美运行。
这是该类:
package com.example.flybase2;
import android.app.Activity;
import android.app.Dialog;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class viewEdit extends Activity implements OnClickListener{
EditText namePassedEdit;
EditText numPassedEdit;
EditText emailPassedEdit;
EditText commentPassedEdit;
Button bUpdate;
Button bDelete;
long passedID = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.editview);
DBHandler displayEdit = new DBHandler(this, null, null);
Bundle extras = getIntent().getExtras();
if (extras != null) {
passedID = extras.getLong("passedID");
}
displayEdit.open();
String returnedNameToEdit = displayEdit.getName(passedID);
String returnedNumToEdit = displayEdit.getNum(passedID);
String returnedEmailToEdit = displayEdit.getEmail(passedID);
String returnedCommentToEdit = displayEdit.getComments(passedID);
namePassedEdit = (EditText) findViewById(R.id.inputNameEdit);
numPassedEdit = (EditText) findViewById(R.id.inputTelNoEdit);
emailPassedEdit = (EditText) findViewById(R.id.inputEmailEdit);
commentPassedEdit = (EditText) findViewById(R.id.inputCommentEdit);
bUpdate = (Button) findViewById (R.id.btnAddConEdit);
bDelete = (Button) findViewById (R.id.btnDeleteContact);
namePassedEdit.setText(returnedNameToEdit);
numPassedEdit.setText(returnedNumToEdit);
emailPassedEdit.setText(returnedEmailToEdit);
commentPassedEdit.setText(returnedCommentToEdit);
bUpdate.setOnClickListener(this);
bDelete.setOnClickListener(this);
}
String nameEdit = namePassedEdit.getText().toString();
String telEdit = numPassedEdit.getText().toString();
String emailEdit = emailPassedEdit.getText().toString();
String commentEdit = commentPassedEdit.getText().toString();
@Override
public void onClick(View updateOrDeleteClicked) {
boolean check = true;
switch(updateOrDeleteClicked.getId()){
case (R.id.btnAddConEdit):
try
{
DBHandler updateData = new DBHandler(this, null, null);
updateData.open();
updateData.updateData(passedID, nameEdit, telEdit, emailEdit, commentEdit);
}
catch (Exception e)
{
check = false;
Dialog d = new Dialog(this);
d.setTitle("Contact failed to be deleted.");
TextView txt = new TextView(this);
txt.setText("Fail");
d.setContentView(txt);
d.show();
}
finally
{
if(check = true);
{
Dialog e = new Dialog(this);
e.setTitle("Contact deleted.");
TextView txt = new TextView(this);
txt.setText("Success");
e.setContentView(txt);
e.show();
}
}
break;
case (R.id.btnDeleteContact):
try
{
DBHandler deleteContact = new DBHandler(this, null, null);
deleteContact.open();
deleteContact.deleteData(passedID);
}
catch (Exception e)
{
check = false;
Dialog d = new Dialog(this);
d.setTitle("Contact failed to be deleted.");
TextView txt = new TextView(this);
txt.setText("Fail");
d.setContentView(txt);
d.show();
}
finally
{
if(check = true);
{
Dialog e = new Dialog(this);
e.setTitle("Contact deleted.");
TextView txt = new TextView(this);
txt.setText("Success");
e.setContentView(txt);
e.show();
}
}
break;
}
}
}
最佳答案
String nameEdit = namePassedEdit.getText().toString();
String telEdit = numPassedEdit.getText().toString();
String emailEdit = emailPassedEdit.getText().toString();
String commentEdit = commentPassedEdit.getText().toString();
这些行不在方法内部，您不能那样使用它们。您在 namePassedEdit 上得到一个空指针，因为它在创建类时尝试初始化它们，但尚未为它们分配任何内容。
关于java - try catch - 无法实例化 Activity ComponentInfo，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/14326366/