我有EditViews来提示用户输入最小值和最大值。输入的数据被传递给Activity函数并生成一个随机数。该随机数被传递给另一个要显示的Activity。当我输入最小值和最大值，然后单击生成按钮时，我被引导到一个空白屏幕。但是，我期望显示randValue。

MainActivity.java

public class MainActivity extends AppCompatActivity {
public final static String RAND_NUM = "com.example.random.MESSAGE";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
}

public void generateNum(View view) {
    Intent intent = new Intent(this, DisplayNumActivity.class);

    EditText minInput = (EditText) findViewById(R.id.min_num);
    EditText maxInput = (EditText) findViewById(R.id.max_num);

    int minNum = Integer.parseInt(minInput.getText().toString());
    int maxNum = Integer.parseInt(maxInput.getText().toString());
    Random rand = new Random();
    int randNum = rand.nextInt(maxNum - minNum) + minNum;
    intent.putExtra(RAND_NUM, randNum);
    startActivity(intent);

  }
}

DisplayNumActivity.java

public class DisplayNumActivity extends AppCompatActivity {

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

    Intent intent = getIntent();
    String randValue = intent.getStringExtra(MainActivity.RAND_NUM);

    TextView textView = new TextView(this);
    textView.setTextSize(30);
    textView.setText(randValue);

    ViewGroup layout = (ViewGroup) findViewById(R.id.activity_display_num);
    layout.addView(textView);

  }
}

activity_main. 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:orientation="horizontal"
    tools:context="com.example.random.MainActivity">

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Min number"
    android:id="@+id/textView"
    android:layout_marginTop="40dp"
    android:layout_alignParentTop="true"
    android:layout_alignLeft="@+id/textView2"
    android:layout_alignStart="@+id/textView2" />

<EditText
    android:id="@+id/min_num"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:hint="min"
    android:inputType="number"
    android:layout_marginTop="32dp"
    android:layout_below="@+id/textView"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Max number"
    android:id="@+id/textView2"
    android:layout_marginTop="43dp"
    android:layout_below="@+id/min_num"
    android:layout_centerHorizontal="true" />

<EditText
    android:id="@+id/max_num"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="max"
    android:inputType="number"
    android:minWidth="500dp"
    android:layout_centerVertical="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />

<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/button_text"
    android:onClick="generateNum"
    android:id="@+id/button"
    android:layout_below="@+id/max_num"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="43dp" />