未使用意图打开活动

Question

I am making an app and I need an activity to open up when one of the buttons is pushed. They all open the same activity. I've checked, they all have the right file names and they're all in the manifest, but when I try and click the button to open the activity, it tells me "Unfortunately ... has stopped." Please help me. Here is the Manifest:

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.apps.testp">

<uses-sdk
    android:minSdkVersion="8"
    android:targetSdkVersion="8" />

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >

    <activity
        android:name="com.apps.testp.MainActivityWithButtons"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity
        android:name="com.apps.testp.LocationSelectFromAlertButtons"
        android:label="@string/title_activity_location_select_from_alert_buttons" >
    </activity>

</application>

Here is the MainActivityWithButtons.java:

package com.apps.testp;

import android.support.v7.app.ActionBarActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;


@SuppressWarnings("deprecation")
public class MainActivityWithButtons extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main_activity_with_buttons);

    Button breakIn=(Button)findViewById(R.id.houseBreakIn);
    Button robbery=(Button)findViewById(R.id.storeRobbery);
    Button car=(Button)findViewById(R.id.carTheft);
    Button assaulting=(Button)findViewById(R.id.assault);
    Button shots=(Button)findViewById(R.id.shotsFired);
    Button fight=(Button)findViewById(R.id.fighting);
    Button address=(Button)findViewById(R.id.setOrChangeAddress);


    address.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
            startActivity(i);

        }
    });



    breakIn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
            startActivity(i);
        }
    });



    robbery.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
                startActivity(i);
                }
            });



    car.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
            startActivity(i);
        }
    });


    assaulting.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
            startActivity(i);
        }
    });


    shots.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
            startActivity(i);
        }
    });


    fight.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            Intent i = new Intent(MainActivityWithButtons.this, LocationSelectFromAlertButtons.class);
            startActivity(i);
        }
    });



    //Next Listener Goes Here
}


@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_activity_with_buttons, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

Here is the Activity I'm trying to open:

package com.apps.testp;

    import android.support.v7.app.ActionBarActivity;
    import android.os.Bundle;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.TextView;

    @SuppressWarnings("deprecation")
    public class LocationSelectFromAlertButtons extends ActionBarActivity {

DBAdapter myDB;

Button save=(Button)findViewById(R.id.saveBtn);
TextView currentAddress=(TextView)findViewById(R.id.CurrAddress);
EditText addressNew=(EditText)findViewById(R.id.tbNewAddress);

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_location_select_from_alert_buttons);

    openDB();



}
private void openDB() {
    myDB = new DBAdapter(this);
    myDB.open();
}

@Override
protected void onDestroy() {
    super.onDestroy();
    closeDB();
}

private void closeDB() {

    myDB.close();
}
public void saveButtonClicked(){
    long newId =myDB.insertRow(LocationSelectFromAlertButtons.this.addressNew.getText().toString());


}








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

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

}

ALL help will be greatly appreciated! Thanks guys

Edit:

LogCat:

    07-18 20:01:55.572  21821-21821/com.apps.testp D/dalvikvm? Late-enabling CheckJNI
07-18 20:01:55.572  21821-21821/com.apps.testp D/dalvikvm? Try to disable coredump for pid 21821
07-18 20:01:55.903  21821-21821/com.apps.testp I/dalvikvm? Could not find method android.content.res.TypedArray.getChangingConfigurations, referenced from method android.support.v7.internal.widget.TintTypedArray.getChangingConfigurations
07-18 20:01:55.903  21821-21821/com.apps.testp W/dalvikvm? VFY: unable to resolve virtual method 411: Landroid/content/res/TypedArray;.getChangingConfigurations ()I
07-18 20:01:55.903  21821-21821/com.apps.testp D/dalvikvm? VFY: replacing opcode 0x6e at 0x0002
07-18 20:01:55.903  21821-21821/com.apps.testp I/dalvikvm? Could not find method android.content.res.TypedArray.getType, referenced from method android.support.v7.internal.widget.TintTypedArray.getType
07-18 20:01:55.903  21821-21821/com.apps.testp W/dalvikvm? VFY: unable to resolve virtual method 433: Landroid/content/res/TypedArray;.getType (I)I
07-18 20:01:55.903  21821-21821/com.apps.testp D/dalvikvm? VFY: replacing opcode 0x6e at 0x0002
07-18 20:01:56.112  21821-21821/com.apps.testp D/libEGL? loaded /vendor/lib/egl/libEGL_POWERVR_SGX544_115.so
07-18 20:01:56.143  21821-21821/com.apps.testp D/libEGL? loaded /vendor/lib/egl/libGLESv1_CM_POWERVR_SGX544_115.so
07-18 20:01:56.153  21821-21821/com.apps.testp D/libEGL? loaded /vendor/lib/egl/libGLESv2_POWERVR_SGX544_115.so
07-18 20:01:56.233  21821-21821/com.apps.testp D/OpenGLRenderer? Enabling debug mode 0
07-18 20:01:58.432  21821-21821/com.apps.testp D/AndroidRuntime? Shutting down VM
07-18 20:01:58.432  21821-21821/com.apps.testp W/dalvikvm? threadid=1: thread exiting with uncaught exception (group=0x41abae10)
07-18 20:01:58.432  21821-21821/com.apps.testp E/AndroidRuntime? FATAL EXCEPTION: main
            java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.apps.testp/com.apps.testp.LocationSelectFromAlertButtons}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2171)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
            at android.app.ActivityThread.access$700(ActivityThread.java:150)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5279)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
            at dalvik.system.NativeStart.main(Native Method)
             Caused by: java.lang.NullPointerException
            at android.app.Activity.findViewById(Activity.java:1886)
            at com.apps.testp.LocationSelectFromAlertButtons.<init>(LocationSelectFromAlertButtons.java:17)
            at java.lang.Class.newInstanceImpl(Native Method)
            at java.lang.Class.newInstance(Class.java:1319)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1071)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2162)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2295)
            at android.app.ActivityThread.access$700(ActivityThread.java:150)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1280)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5279)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

Locate this:

Button save=(Button)findViewById(R.id.saveBtn);
TextView currentAddress=(TextView)findViewById(R.id.CurrAddress);
EditText addressNew=(EditText)findViewById(R.id.tbNewAddress);

After your setContentView.

Answer 2

I think the problem may be in your Manifest. You have not set

android:parentActivityName="com.apps.testp.MainActivityWithButtons"

The system uses this to enable up navigation behavior (which users will expect) and I don't know if you can navigate as you intend without including this in your manifest.

To support older devices, also include:

<meta-data android:name="android.support.PARENT_ACTIVITY"
android:value="com.apps.testp.MainActivityWithButtons" />

within the body of your activity declaration.

For more information, see http://developer.android.com/training/basics/firstapp/starting-activity.html .

I have previously followed the guide at developer.android.com to implement such a function without issue.

Answer 3

The problem is here:

Caused by: java.lang.NullPointerException
            at android.app.Activity.findViewById(Activity.java:1886)

Which is caused by calling findViewById() before you have a valid Context in your Activity.

When you call findViewById() , it's actually short for this.findViewById() , and in your case, this is null, hence the NullPointerException.

Note that in order to find the Buttons, the correct layout needs to be inflated into the window, so you need to place these calls after setContentView() as well:

Button save;
TextView currentAddress;
EditText addressNew;

@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_location_select_from_alert_buttons);

    save = (Button)findViewById(R.id.saveBtn);
    currentAddress = (TextView)findViewById(R.id.CurrAddress);
    addressNew = (EditText)findViewById(R.id.tbNewAddress);

    openDB();

}