java - Java 应用程序崩溃 (NullPointerException)

Question

我只是在编写密码管理器，但每次我运行它时，它都会因 NullPointerException 而崩溃。我检查了代码，但我是新开发人员。这里有人知道为什么吗？:(

MainActivity.java 的代码：

package de.lennartschoch.passwordmanager;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {

Button login;
EditText masterpassfield;
static String masterpass;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    login = (Button) findViewById(R.id.login);
    masterpass = "";
    masterpassfield = (EditText) findViewById(R.id.masterpass);

    if(masterpass.equals("")) {

        Intent intent = new Intent(this,NewMasterpass.class);
        startActivity(intent);
        return;
    }

    login.setOnClickListener(new OnClickListener() {


        @Override
        public void onClick(View view) {

            if(masterpassfield.getText().toString().equals(masterpass)) {

                Intent success = new Intent(view.getContext(), Passwords.class);
                startActivityForResult(success, 0);

            }

        }});
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.activity_main, menu);
    return true;
}

}

NewMasterpass.java 的代码：

package de.lennartschoch.passwordmanager;

import android.app.Activity;
import android.content.Intent;
import android.graphics.Color;
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 NewMasterpass extends Activity {

EditText masterpasscreate;
EditText repeat;
Button finish;
TextView mistake;

/** Called when the activity is first created. */
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_new_masterpass);

    masterpasscreate = (EditText) findViewById(R.id.masterpasscreate);
    repeat = (EditText) findViewById(R.id.repeatcreate);
    finish = (Button) findViewById(R.id.finish);
    mistake = (TextView) findViewById(R.id.mistake);

    finish.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View view) {

            if(!masterpasscreate.getText().toString().equals(repeat.getText().toString())) {

                mistake.setText("The passwords are different.");
                mistake.setTextColor(Color.RED);

            }
            else if(masterpasscreate.getText().toString().equals("") || repeat.getText().toString().equals("")) {

                mistake.setText("Both textfields must be filled in");
                mistake.setTextColor(Color.RED);

            }
            else {

                MainActivity.masterpass = masterpasscreate.getText().toString();
                Intent myIntent = new Intent(view.getContext(), MainActivity.class);
                startActivityForResult(myIntent, 0);
            }

        }});


}
}

LogCat 错误：

01-20 17:17:52.629: D/AndroidRuntime(561): Shutting down VM
01-20 17:17:52.629: W/dalvikvm(561): threadid=1: thread exiting with uncaught exception         (group=0x409961f8)
01-20 17:17:52.639: E/AndroidRuntime(561): FATAL EXCEPTION: main
01-20 17:17:52.639: E/AndroidRuntime(561): java.lang.RuntimeException: Unable to start activity         ComponentInfo{de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.MainActivit    y}: java.lang.NullPointerException
01-20 17:17:52.639: E/AndroidRuntime(561):  at     android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.os.Looper.loop(Looper.java:137)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.ActivityThread.main(ActivityThread.java:4340)
01-20 17:17:52.639: E/AndroidRuntime(561):  at java.lang.reflect.Method.invokeNative(Native Method)
01-20 17:17:52.639: E/AndroidRuntime(561):  at java.lang.reflect.Method.invoke(Method.java:511)
01-20 17:17:52.639: E/AndroidRuntime(561):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-20 17:17:52.639: E/AndroidRuntime(561):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-20 17:17:52.639: E/AndroidRuntime(561):  at dalvik.system.NativeStart.main(Native Method)
01-20 17:17:52.639: E/AndroidRuntime(561): Caused by: java.lang.NullPointerException
01-20 17:17:52.639: E/AndroidRuntime(561):  at de.lennartschoch.passwordmanager.MainActivity.onCreate(MainActivity.java:26)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.Activity.performCreate(Activity.java:4465)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
01-20 17:17:52.639: E/AndroidRuntime(561):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
01-20 17:17:52.639: E/AndroidRuntime(561):  ... 11 more
01-20 17:17:57.129: I/Process(561): Sending signal. PID: 561 SIG: 9
01-20 17:21:37.499: D/AndroidRuntime(608): Shutting down VM
01-20 17:21:37.499: W/dalvikvm(608): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
01-20 17:21:37.511: E/AndroidRuntime(608): FATAL EXCEPTION: main
01-20 17:21:37.511: E/AndroidRuntime(608): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.MainActivity}: android.content.ActivityNotFoundException: Unable to find explicit activity class {de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.NewMasterpass}; have you declared this activity in your AndroidManifest.xml?
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.os.Looper.loop(Looper.java:137)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.ActivityThread.main(ActivityThread.java:4340)
01-20 17:21:37.511: E/AndroidRuntime(608):  at java.lang.reflect.Method.invokeNative(Native Method)
01-20 17:21:37.511: E/AndroidRuntime(608):  at java.lang.reflect.Method.invoke(Method.java:511)
01-20 17:21:37.511: E/AndroidRuntime(608):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-20 17:21:37.511: E/AndroidRuntime(608):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-20 17:21:37.511: E/AndroidRuntime(608):  at dalvik.system.NativeStart.main(Native Method)
01-20 17:21:37.511: E/AndroidRuntime(608): Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.NewMasterpass}; have you declared this activity in your AndroidManifest.xml?
01-20 17:21:37.511: E/AndroidRuntime(608):  at  android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1508)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.Instrumentation.execStartActivity(Instrumentation.java:1384)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.Activity.startActivityForResult(Activity.java:3190)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.Activity.startActivity(Activity.java:3297)
01-20 17:21:37.511: E/AndroidRuntime(608):  at de.lennartschoch.passwordmanager.MainActivity.onCreate(MainActivity.java:30)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.Activity.performCreate(Activity.java:4465)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
01-20 17:21:37.511: E/AndroidRuntime(608):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
01-20 17:21:37.511: E/AndroidRuntime(608):  ... 11 more
01-20 17:22:30.769: D/AndroidRuntime(655): Shutting down VM
01-20 17:22:30.769: W/dalvikvm(655): threadid=1: thread exiting with uncaught exception (group=0x409961f8)
01-20 17:22:30.779: E/AndroidRuntime(655): FATAL EXCEPTION: main
01-20 17:22:30.779: E/AndroidRuntime(655): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.MainActivity}: android.content.ActivityNotFoundException: Unable to find explicit activity class {de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.NewMasterpass}; have you declared this activity in your AndroidManifest.xml?
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.ActivityThread.access$600(ActivityThread.java:122)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.os.Looper.loop(Looper.java:137)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.ActivityThread.main(ActivityThread.java:4340)
01-20 17:22:30.779: E/AndroidRuntime(655):  at java.lang.reflect.Method.invokeNative(Native Method)
01-20 17:22:30.779: E/AndroidRuntime(655):  at java.lang.reflect.Method.invoke(Method.java:511)
01-20 17:22:30.779: E/AndroidRuntime(655):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
01-20 17:22:30.779: E/AndroidRuntime(655):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
01-20 17:22:30.779: E/AndroidRuntime(655):  at dalvik.system.NativeStart.main(Native Method)
01-20 17:22:30.779: E/AndroidRuntime(655): Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.NewMasterpass}; have you declared this activity in your AndroidManifest.xml?
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1508)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.Instrumentation.execStartActivity(Instrumentation.java:1384)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.Activity.startActivityForResult(Activity.java:3190)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.Activity.startActivity(Activity.java:3297)
01-20 17:22:30.779: E/AndroidRuntime(655):  at de.lennartschoch.passwordmanager.MainActivity.onCreate(MainActivity.java:30)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.Activity.performCreate(Activity.java:4465)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
01-20 17:22:30.779: E/AndroidRuntime(655):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
01-20 17:22:30.779: E/AndroidRuntime(655):  ... 11 more
01-20 17:22:33.180: I/Process(655): Sending signal. PID: 655 SIG: 9

score 1 · Accepted Answer

它问：

01-20 17:22:30.779: E/AndroidRuntime(655): java.lang.RuntimeException: Unable to start activity ComponentInfo{de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.MainActivity}: android.content.ActivityNotFoundException: Unable to find explicit activity class {de.lennartschoch.passwordmanager/de.lennartschoch.passwordmanager.NewMasterpass}; 

have you declared this activity in your AndroidManifest.xml?

你？

score 0 · Accepted Answer

0

在您的清单 xml 中声明NewMasterPass活动，如 logcat 中明确提到的！

于 2013-01-20T17:39:38.643 回答

score 0 · Accepted Answer

尝试将此添加到您的 AndroidManifest.xml

<activity android:name="de.lennartschoch.passwordmanager.NewMasterpass" />

java - Java 应用程序崩溃 (NullPointerException)

3 回答 3

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