条件意图不起作用

时间:2018-02-28 11:10:49

标签: java android android-intent

我试过搜索这个主题,但我找不到任何可以帮助我的东西,所以我在这里问这个。

我是初学者,所以我不理解很多术语,如果你回答我的问题,请尝试使用简单的语言让我明白。

我的条件是两个列表中相同位置的元素进行比较,如果它们不等于跳转到另一个活动:

if (randomColors.get(i) != userColors.get(i)) {
    Intent i = new Intent( GameActivity.this, GameOverActivity.class);
    startActivity(i);
}

它在调试中显示一个我无法解决的错误:

  

java.lang.RuntimeException:无法启动活动ComponentInfo {com.gabie212.simonsays / com.gabie212.simonsays.GameOverActivity}:java.lang.NullPointerException:尝试调用虚方法' void android.view。 View.setOnClickListener(android.view.View $ OnClickListener)'在空对象引用上

请帮助我,我是初学者,而且我不知道我的代码有什么问题,因为我完全按照他们在课堂上教给我们的那样做了...

这是完整的代码 我知道它不是最好的,但它在proggress中的作品

    package com.gabie212.simonsays;

    import android.content.Context;
    import android.content.Intent;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.Toast;

    import java.util.ArrayList;

    public class GameActivity extends AppCompatActivity implements 
    View.OnClickListener {

private int i = 0;
private Thread t = new Thread();
private Button greenButton;
private Button redButton;
private Button blueButton;
private Button yellowButton;
private Button startButton;

private ArrayList<Integer> randomColors = new ArrayList<Integer>();
private ArrayList<Integer> userColors = new ArrayList<Integer>();

private GameManger gm;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    gm =  new GameManger(this);

    setContentView(R.layout.activity_game);
    greenButton = (Button) findViewById(R.id.btnGreen);
    redButton = (Button) findViewById(R.id.btnRed);
    blueButton = (Button) findViewById(R.id.btnBlue);
    yellowButton = (Button) findViewById(R.id.btnYellow);
    startButton = (Button) findViewById(R.id.btnStart);
    startButton.setOnClickListener(this);
    greenButton.setOnClickListener(this);
    redButton.setOnClickListener(this);
    blueButton.setOnClickListener(this);
    yellowButton.setOnClickListener(this);





}

@Override
public void onClick(View v) {

    int num;

    num= gm.getColor(4);
    randomColors.add(num);


    android.os.Handler handler = new android.os.Handler();
    //TODO if the start button is pressed multiple times simultaneously it starts the lightup loop multiple times simultaneously
    if (v.getId() == startButton.getId()) {
        for (i = 0; i < randomColors.size(); i++) //light up loop
        {
            switch (randomColors.get(i)) {
                case 1:
                    greenButton.setBackgroundResource(R.drawable.greenlightup);

                    handler.postDelayed(new Runnable()
                    {

                        @Override
                        public void run() {
                            // TODO Auto-generated method stub
                            greenButton.setBackgroundResource(R.drawable.green);
                        }
                    }, 2000);


                    break;
                case 2:
                    redButton.setBackgroundResource(R.drawable.redlightup);
                    handler.postDelayed(new Runnable()
                    {

                        @Override
                        public void run() {
                            // TODO Auto-generated method stub
                            redButton.setBackgroundResource(R.drawable.red);
                        }
                    }, 2000);


                    break;
                case 3:
                    blueButton.setBackgroundResource(R.drawable.bluelightup);
                    handler.postDelayed(new Runnable()
                    {

                        @Override
                        public void run() {
                            // TODO Auto-generated method stub
                            blueButton.setBackgroundResource(R.drawable.blue);
                        }
                    }, 2000);


                    break;
                case 4:
                    yellowButton.setBackgroundResource(R.drawable.yellowlightup);
                    handler.postDelayed(new Runnable()
                    {

                        @Override
                        public void run() {
                            // TODO Auto-generated method stub
                            yellowButton.setBackgroundResource(R.drawable.yellow);
                        }
                    }, 2000);


                    break;
            }
            handler.postDelayed(new Runnable()
            {
                public void run() {
                }

            }, 2000);
        }

        for(i=0;i<randomColors.size();i++)
        {

            if(v.getId()==greenButton.getId())
            {
                userColors.add(1);
            }
            else
            {
                if(v.getId()==redButton.getId()){
                    userColors.add(2);
                }
                else
                {
                    if(v.getId()==blueButton.getId())
                    {
                        userColors.add(3);
                    }
                    else
                    {
                        userColors.add(4);
                    }
                }


            }


        }
        for(i=0;i<randomColors.size();i++)
        {
            if(randomColors.get(i)!=userColors.get(i))
            {

                Intent i = new Intent( GameActivity.this, GameOverActivity.class);
                startActivity(i);
            }
        }



    }

}
}

它不是一个简单的空指针异常,至少我不这么认为,因为这里没有任何东西是空的,if语句中只有一个简单的意图

这里是游戏活动的代码

    package com.gabie212.simonsays;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;
import android.view.View;



    public class GameOverActivity extends AppCompatActivity implements View.OnClickListener  {

    private Button againButton;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_game_over);
        againButton = (Button) findViewById(R.id.btnStart);
        againButton.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {

        Intent in = new Intent(GameOverActivity.this, GameActivity.class);
        startActivity(in);
    }
    }

提前致谢。

1 个答案:

答案 0 :(得分:0)

GameOverActivity,在这一行:

againButton = (Button) findViewById(R.id.btnStart);

当您从主要活动布局(againButton)引用null时,btnStartactivity_game.xml。由于GameOverActivity正在使用activity_game_over.xml进行布局,因此找不到此内容:

setContentView(R.layout.activity_game_over);

任何视图都需要在activity_game_over.xml文件中定义,以供活动使用。您需要引用layout/activity_game_over.xml

中定义的按钮ID
againButton = (Button) findViewById(R.id.btnAgain); // Or whatver you've named it

关于Intent无法正常工作的具体问题,Intent本身工作正常,只是GameOverActivity无法正常启动上述问题,因此您的应用程序崩溃。