Question

当我尝试将一个整数从一个活动传递到另一个活动时，应用程序会崩溃。一切正常。方法和开始一个新的活动。这是我的代码：

import android.content.Intent;
import android.os.Bundle;


public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if (android.os.Build.VERSION.SDK_INT > 9) {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);
    }

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}


public int URLi() {
.
./code
.
.
.
    return celsius;
}

public void onclick (View v) {
    int temp=URLi(v);
    Intent intent = new Intent(this, TheTemp.class);
    intent.putExtra("temp",temp);
    startActivity(intent);
}

}

新活动

public class TheTemp extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_the_temp);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
}

Intent intent = getIntent();
int receiveValue = getIntent().getIntExtra("temp",0);

}

清单

<?xml version="1.0" encoding="utf-8"?>

<uses-permission android:name="android.permission.INTERNET" />

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">
    <activity
        android:name=".MainActivity"
        android:label="@string/app_name"
        android:theme="@style/AppTheme.NoActionBar">
        <intent-filter>

            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
    <activity
        android:name=".TheTemp"
        android:label="@string/title_activity_the_temp"
        android:theme="@style/AppTheme.NoActionBar"></activity>
</application>

以及我得到的错误：

05-25 16:05:01.047 11632-11632/com.example.owner.MYproject E/AndroidRuntime: FATAL EXCEPTION: main
                                                                             Process: com.example.owner.MYproject, PID: 11632
                                                                             java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.Owner.MYproject/com.example.Owner.Myproject.TheTemp}: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.content.Intent.getIntExtra(java.lang.String, int)' on a null object reference
                                                                                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2282)
                                                                                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2439)
                                                                                 at android.app.ActivityThread.access$800(ActivityThread.java:162)
                                                                                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1348)
                                                                                 at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                                 at android.os.Looper.loop(Looper.java:135)
                                                                                 at android.app.ActivityThread.main(ActivityThread.java:5421)
                                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                                 at java.lang.reflect.Method.invoke(Method.java:372)
                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:914)
                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:707)

谢谢你的帮助！

Answer 1

获取onCreate()方法中的值。目前，您正在方法之外获取它。

public class TheTemp extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_the_temp);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });

    Intent intent = getIntent(); 
    int receiveValue = getIntent().getIntExtra("temp",0);
}
}

如何在活动之间传递一个整数？

1 个答案: