我不断收到错误“无法实例化活动 ComponentInfo{com.game.yugioh/com.game.yugioh.MainActivity}：java.lang.NullPointerException”，我不知道如何解决它。
日志猫：
10-19 16:03:39.889 17612-17612/com.game.yugioh E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.game.yugioh/com.game.yugioh.MainActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2240)
at android.app.ActivityThread.access$600(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1262)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:4987)
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:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at android.app.Activity.findViewById(Activity.java:1851)
at com.game.yugioh.MainActivity.<init>(MainActivity.java:12)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1319)
at android.app.Instrumentation.newActivity(Instrumentation.java:1039)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2240)
at android.app.ActivityThread.access$600(ActivityThread.java:139)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1262)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:156)
at android.app.ActivityThread.main(ActivityThread.java:4987)
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:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
MainActivity.java：
package com.game.yugioh;
import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.view.Menu;
import android.widget.ImageView;
public class MainActivity extends Activity {
Bitmap[] hand;
ImageView handCard1 = (ImageView) findViewById(R.id.handCard1);
ImageView handCard2 = (ImageView) findViewById(R.id.handCard2);
ImageView handCard3 = (ImageView) findViewById(R.id.handCard3);
ImageView handCard4 = (ImageView) findViewById(R.id.handCard4);
ImageView handCard5 = (ImageView) findViewById(R.id.handCard5);
ImageView handCard6 = (ImageView) findViewById(R.id.handCard6);
Deck synchronWarriorsDeck = new Deck("Synchron Warriors");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
start();
}
@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, menu);
return true;
}
private void start() {
for (int i = 0; i < 5; i++) {
Field.draw();
addHandCard();
}
}
private void addHandCard() {
int location = Field.getHandCounter();
String next = String.valueOf(Field.getNext());
if (location == 1) {
handCard1.setImageResource(getResources().getIdentifier(next, "drawable", getPackageName()));
} else if (location == 2) {
handCard2.setImageResource(getResources().getIdentifier(next, "drawable", getPackageName()));
} else if (location == 3) {
handCard3.setImageResource(getResources().getIdentifier(next, "drawable", getPackageName()));
} else if (location == 4) {
handCard4.setImageResource(getResources().getIdentifier(next, "drawable", getPackageName()));
} else if (location == 5) {
handCard5.setImageResource(getResources().getIdentifier(next, "drawable", getPackageName()));
} else if (location == 6) {
handCard6.setImageResource(getResources().getIdentifier(next, "drawable", getPackageName()));
}
}
}
字段.java：
package com.game.yugioh;
import java.util.Arrays;
import java.util.List;
public class Field {
private static String name = Deck.getName();
private static int originalSize;
private static int currentSize;
private static int handCounter = 0;
private static int deckCounter = 0;
private static List<String[]> deck = Arrays.asList(Deck.synchronWarriors());
private static int check = 0;
private static int handLocation;
private Field() {
originalSize = 0;
currentSize = 0;
}
public static int getOriginalSize() {
if (name.equals("Synchron Warriors")) {
originalSize = Deck.synchronWarriors().length;
}
return originalSize;
}
public static int getCurrentSize() {
if (name.equals("Synchron Warriors")) {
currentSize = originalSize - deckCounter;
}
return currentSize;
}
public static void draw() {
getNext();
handCounter++;
deckCounter++;
}
public static int getHandCounter() {
return handCounter;
}
public int getDeckCounter() {
return deckCounter;
}
public static String[] getNext() {
int idx = deck.indexOf(deckCounter);
if (idx < 0 || idx == deck.size())
return null;
return deck.get(idx);
}
}
甲板.java：
package com.game.yugioh;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class Deck {
private static String name;
private static String firstCard;
private static String[][] synchronWarriors;
private static List<String[]> deck = Arrays.asList(synchronWarriors);
public Deck(String n) {
name = n;
}
public static String getName() {
if (name.equals("Synchron Warriors")) {
firstCard = synchronWarriors[0][0];
if (firstCard.equals("Changer Synchron")) {
name = "Synchron Warriors";
}
}
return name;
}
public void shuffle() {
Collections.shuffle(Arrays.asList(synchronWarriors));
}
public static String[][] synchronWarriors() {
String[][] synchronWarriors = {{"changer_synchron", "changer_synchron", "dandylion", "junk_synchron", "junk_synchron",
"junk_synchron", "level_eater", "level_eater", "level_eater", "quickdraw_synchron", "quickdraw_synchron",
"quickdraw_synchron", "quillbolt_hedgehog", "quillbolt_hedgehog", "quillbolt_hedgehog", "synchron_explorer",
"synchron_explorer", "synchron_explorer", "tuningware", "tuningware", "tuningware", "turbo_synchron",
"turbo_synchron", "unknown_synchron"},
{"dark_hole", "mind_control", "mst", "mst", "scapegoat", "tuning", "tuning", "tuning"},
{"bottomless_trap_hole", "call_of_the_haunted", "call_of_the_haunted", "call_of_the_haunted", "limit_reverse",
"limit_reverse", "limit_reverse", "mirror_force", "mirror_force", "solen_warning", "starlight_road",
"starlight_road"}};
return synchronWarriors;
}
}
活动主.xml：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<ImageView
android:id="@+id/opponentHandCard1"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignParentEnd="false"
android:contentDescription="opponent_card1_in_hand"
android:src="@drawable/card_back" />
<ImageView
android:id="@+id/opponentHandCard2"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentHandCard1"
android:layout_toRightOf="@+id/opponentHandCard1"
android:contentDescription="opponent_card2_in_hand"
android:src="@drawable/card_back" />
<ImageView
android:id="@+id/opponentHandCard3"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentHandCard2"
android:layout_toRightOf="@+id/opponentHandCard2"
android:contentDescription="opponent_card3_in_hand"
android:src="@drawable/card_back" />
<ImageView
android:id="@+id/opponentHandCard4"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentHandCard3"
android:layout_toRightOf="@+id/opponentHandCard3"
android:contentDescription="opponent_card4_in_hand"
android:src="@drawable/card_back" />
<ImageView
android:id="@+id/opponentHandCard5"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentHandCard4"
android:layout_toRightOf="@+id/opponentHandCard4"
android:contentDescription="opponent_card5_in_hand"
android:src="@drawable/card_back" />
<ImageView
android:id="@+id/opponentHandCard6"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentHandCard5"
android:layout_toRightOf="@+id/opponentHandCard5"
android:contentDescription="opponent_card6_in_hand"
android:src="@drawable/card_back" />
<ImageView
android:id="@+id/handCard1"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignLeft="@+id/opponentHandCard1"
android:layout_alignParentBottom="true"
android:layout_marginBottom="11dp"
android:src="@drawable/card_back"
android:onClick="onClickHandCard1" />
<ImageView
android:id="@+id/handCard2"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/handCard1"
android:layout_toRightOf="@+id/handCard1"
android:src="@drawable/card_back"
android:onClick="onClickHandCard2" />
<ImageView
android:id="@+id/handCard3"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/handCard2"
android:layout_toRightOf="@+id/handCard2"
android:src="@drawable/card_back"
android:onClick="onClickHandCard3" />
<ImageView
android:id="@+id/handCard4"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/handCard3"
android:layout_toRightOf="@+id/handCard3"
android:src="@drawable/card_back"
android:onClick="onClickHandCard4" />
<ImageView
android:id="@+id/handCard5"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignBottom="@+id/handCard4"
android:layout_toRightOf="@+id/handCard4"
android:src="@drawable/card_back"
android:onClick="onClickHandCard5" />
<ImageView
android:id="@+id/handCard6"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/handCard5"
android:layout_toRightOf="@+id/handCard5"
android:src="@drawable/card_back"
android:onClick="onClickHandCard6" />
<ImageView
android:id="@+id/opponentSpellTrapZone1"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignLeft="@+id/opponentHandCard1"
android:layout_below="@+id/opponentHandCard1"
android:layout_marginTop="19dp" />
<ImageView
android:id="@+id/opponentSpellTrapZone2"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignBottom="@+id/opponentSpellTrapZone1"
android:layout_toRightOf="@+id/opponentSpellTrapZone1" />
<ImageView
android:id="@+id/opponentSpellTrapZone3"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentSpellTrapZone2"
android:layout_toRightOf="@+id/opponentSpellTrapZone2" />
<ImageView
android:id="@+id/opponentSpellTrapZone4"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentSpellTrapZone3"
android:layout_toRightOf="@+id/opponentSpellTrapZone3" />
<ImageView
android:id="@+id/opponentSpellTrapZone5"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignTop="@+id/opponentSpellTrapZone4"
android:layout_toRightOf="@+id/opponentSpellTrapZone4" />
<ImageView
android:id="@+id/opponentMonsterZone1"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignLeft="@+id/opponentSpellTrapZone1"
android:layout_below="@+id/opponentSpellTrapZone1" />
<ImageView
android:id="@+id/opponentMonsterZone3"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentSpellTrapZone2"
android:layout_toRightOf="@+id/opponentSpellTrapZone2" />
<ImageView
android:id="@+id/opponentMonsterZone4"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentSpellTrapZone3"
android:layout_toRightOf="@+id/opponentSpellTrapZone3" />
<ImageView
android:id="@+id/opponentMonsterZone5"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentSpellTrapZone4"
android:layout_toRightOf="@+id/opponentSpellTrapZone4" />
<ImageView
android:id="@+id/opponentMonsterZone2"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentSpellTrapZone2"
android:layout_toRightOf="@+id/opponentSpellTrapZone1" />
<ImageView
android:id="@+id/monsterZone1"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignLeft="@+id/opponentMonsterZone1"
android:layout_below="@+id/opponentMonsterZone1" />
<ImageView
android:id="@+id/spellTrapZone1"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignLeft="@+id/monsterZone1"
android:layout_below="@+id/monsterZone1" />
<ImageView
android:id="@+id/monsterZone2"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_above="@+id/spellTrapZone1"
android:layout_toRightOf="@+id/monsterZone1" />
<ImageView
android:id="@+id/monsterZone3"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentMonsterZone3"
android:layout_toRightOf="@+id/opponentMonsterZone2" />
<ImageView
android:id="@+id/monsterZone4"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentMonsterZone3"
android:layout_toRightOf="@+id/opponentMonsterZone3" />
<ImageView
android:id="@+id/monsterZone5"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/opponentMonsterZone5"
android:layout_toRightOf="@+id/opponentMonsterZone4" />
<ImageView
android:id="@+id/spellTrapZone2"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/monsterZone1"
android:layout_toRightOf="@+id/monsterZone1" />
<ImageView
android:id="@+id/spellTrapZone3"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/monsterZone2"
android:layout_toRightOf="@+id/monsterZone2" />
<ImageView
android:id="@+id/spellTrapZone4"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/monsterZone3"
android:layout_toRightOf="@+id/monsterZone3" />
<ImageView
android:id="@+id/spellTrapZone5"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_below="@+id/monsterZone4"
android:layout_toRightOf="@+id/monsterZone4" />
<ImageButton
android:id="@+id/deckZone"
android:layout_width="45dp"
android:layout_height="75dp"
android:layout_alignBottom="@+id/monsterZone5"
android:layout_alignParentRight="true"
android:layout_marginBottom="14dp"
android:onClick="onClickDeckZone" />
--android:src="@drawable/deck" />
<TextView
android:id="@+id/txtDeckNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="44"
android:textAppearance="?android:attr/textAppearanceLarge"
android:layout_below="@+id/deckZone"
android:layout_alignLeft="@+id/deckZone"/>
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignTop="@+id/opponentSpellTrapZone2"
android:layout_marginTop="20dp"
android:layout_toLeftOf="@+id/opponentSpellTrapZone4"
android:text="TextView" />
</RelativeLayout>