动态putExtra（）和getExtra（）

Question

I have 3 activities : 1 main activity with some methods to calculate xy and z positions, and the 3 activities are floors which will switch depending on the value of z.

When I go from activity A (main activity) to B it seems like the datas i've used saved with putExtra and getExtra are frozen to their initial value (ie at the 1st putExtra). Is it normal ? If so do you have any idea as to how I should access dynamically x, y, z from another activity?

In the code i'll show you x,y and z are calculated in the loop that's just for testing. Otherwise I have other methods to calculate them (using WiFi RSSI and a Gradient Descent algorithm)

MainActivity

    public class MainActivity extends AppCompatActivity {
           ImageView myImageView;
           int i = 0;
           int z = 1;
           int x,y,f=1;
           final int imageWidth = 930;
           final int imageHeight = 560;
           private Timer timer;
           int flag_activity=1;

[....] Intent Initialisation

    final Intent intent0 = new android.content.Intent(this, Rdc.class);
    final Intent intent2 = new android.content.Intent(this, r2.class);
    intent0.putExtra("X", i);
    intent0.putExtra("Y", i);
    intent0.putExtra("Z", f);

    intent2.putExtra("X", i);
    intent2.putExtra("Y", i);
    intent2.putExtra("Z", f);


    myImageView = (ImageView) findViewById(R.id.imageView);
    VectorDrawableCompat vectorDrawable = VectorDrawableCompat.create(getResources(), R.drawable.ic_android_black_24dp, null);
    myImageView.setImageDrawable(vectorDrawable);

//....

Loop to update image and change activities depending on the value of f:

    Timer T=new Timer();
    T.scheduleAtFixedRate(new TimerTask() {
        @Override
        public void run() {
            runOnUiThread(new Runnable()
            {
                @Override
                public void run()
                {
                    i++;
                    i=i%10;
                    if(i==7) {f++; f=f%3;}
                    updateTextView(i,i,f);


                    if(f==1) {
                        myImageView.setTranslationX(i * imageWidth / 10);
                        myImageView.setTranslationY(i * imageHeight / 10);
                        flag_activity=1;
                    }
                    else {
                        if(f==2&&flag_activity!=2) {startActivity(intent2); flag_activity=2;}
                        else {
                            if(f==0&&flag_activity!=0) {startActivity(intent0); flag_activity=0;}
                        }                        }


                }
            });
        }
    }, 1000, 1000);

Another activity (the 2 other are the same aside from some resources).

public class r2 extends AppCompatActivity {
ImageView myImageView;
int imageWidth=930;
int imageHeight=560;
int x,y,z;


public void updateTextView(int a, int b, int c) {
    String str="x :"+Integer.toString(a)+"y :"+Integer.toString(b)+"f :"+Integer.toString(c);
    TextView textView = (TextView) findViewById(R.id.textView3);
    textView.setText(str);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_r2);

    myImageView = (ImageView) findViewById(R.id.imageView);
    VectorDrawableCompat vectorDrawable = VectorDrawableCompat.create(getResources(), R.drawable.ic_android_black_24dp, null);
    myImageView.setImageDrawable(vectorDrawable);


    Timer T2=new Timer();
    T2.scheduleAtFixedRate(new TimerTask() {
        @Override
        public void run() {
            runOnUiThread(new Runnable()
            {
                @Override
                public void run()
                {

                    x = getIntent().getIntExtra("X",1);
                    y = getIntent().getIntExtra("Y",1);
                    z = getIntent().getIntExtra("Z",1);
                    updateTextView(x,y,z);

                    if(z==2) {

                        myImageView.setTranslationX(x * imageWidth / 10);
                        myImageView.setTranslationY(y * imageHeight / 10);
                    }
                    else {
                        finish();
                    }
                }
            });
        }
    }, 1000, 1000);



}

}

Answer 1

Not sure how you are putting the extras in the intent. But I will show you how you should do it

Intent intentForActivityB = new Intent(this,ActivityB.class);
intentForActivityB.putExtra("YourKey","Your data")
startActivity(intentForActivityB);

Inside ActivityB
intent.getIntExtra("YourKey",defaultValue);

So maybe in your case, the data is not frozen its just giving you default value.

Answer 2

It's better to use bundle when you try to pass multiple data to another activity.

First create a bundle object

Bundle bundle = new Bundle();
bundle.putString("key1", "string data");
bundle.putInt("key2",12345);

Then pass your bundle with intent. Be careful you will have to use putExtras not putExtra

Intent intent = new Intent(context, destinationClass);
intent.putExtras(bundle);

and then start the intent

context.startActivity(intent);

On the destination class you can receive the bundle with getExtras

Bundle bundle =getIntent().getExtras();

And from that bundle you can extract your data

String yourStringData = 
bundle.getString("key1");
int youtIntData = bundle.getInt("key2");

Bundle supports many data types. Please check the bundle documentation for more details