传递 ArrayList<Double> 到另一个班级

Question

I can read and save a textfile to an Arraylist with my code. Now I want to use this Arraylist in other activities but I have problems with passing the Arraylist to another class. I tried it with intent but it didnt work. I will add the codes of my program below.

Intent intent=new Intent(this, ergebnisse.class);
intent.putExtra("NEFZ", Nlist);
startActivity(intent);

I hope you can help me.

My first activity:

public class NEFZ2array extends AppCompatActivity implements Serializable {

public static void main(String[] args) {
    FileReader file = null;
    try {
        file = new FileReader("NEFZ.txt");
    } catch (FileNotFoundException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }
    ArrayList<Double> Nlist = new ArrayList<Double>();
    int i=0;
    Double d= null;
    try {
        BufferedReader input = new BufferedReader(file);
        String s=null;
        while((s=input.readLine())!=null) {
            StringTokenizer st = new StringTokenizer(s,",");
            while(st.hasMoreTokens()) {
                try {
                    d = Double.parseDouble(st.nextToken());
                } catch (Exception e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                Nlist.add(i, d);
            }
        }
        input.close();
    } catch(Exception e) {
        e.printStackTrace();
    }
    for(double j:Nlist) {
        System.out.println(j);
    }
}

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_nefz2array);

}
}

My Receiver Activity:

public class ergebnisse extends AppCompatActivity implements Serializable {

public Button button_ausfuerlicher;
public Button button_home;

public void init(){
    button_ausfuerlicher = (Button) findViewById(R.id.button_ausfuerlicher);
    button_ausfuerlicher.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Intent intent = new Intent(ergebnisse.this, ausfuehrlicher.class);

            startActivity(intent);
        }
    });
}

public void init2(){
    button_home = (Button) findViewById(R.id.button_home);
    button_home.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Intent intent = new Intent(ergebnisse.this, MainActivity.class);

            startActivity(intent);
        }
    });
}

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_ergebnisse);
    this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE);

    init();
    init2();
}
}

Answer 1

You need to call getIntent() in your receiver activity.

Intent intent = getIntent();

and then you can call

intent.getExtras()

Answer 2

The entry point to an android application is typically the onCreate method.

I suspect that your main method (traditional java entry point) is not being run. You could try calling it from the onCreate, but should really rename it.

To receive an Intent, which should be sent as long as you call your main and add the Intent code, make sure the receiver overrides onReceive.

@Override
public void onReceive(Context context, Intent intent) {
    ArrayList<Double> NEFZ = intent.getExtras().getString("NEFZ");
}

Answer 3

To receive the double array list in the receiver activity you can use:

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ergebnisse);
        this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_SENSOR_LANDSCAPE);

        // Get double list from sender activity
        List<Double> doubleList = (ArrayList<Double>) getIntent().getSerializableExtra("NEFZ");

        // TODO: Process your double list here

        init();
        init2();
}