Question

我在我的应用程序中需要帮助，当按下主页按钮时显示吐司，按下后退按钮并检查手机是否有导航栏

MainActivity.java

package com.example.myapp;

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

public class MainActivity extends Activity {

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {

    if ((keyCode == KeyEvent.KEYCODE_HOME)) {
        Toast.makeText(getApplicationContext(), "goodbye! (home button pressed)", Toast.LENGTH_LONG).show(); //doesn't work here
        finish();
        return true;
    }
    if ((keyCode == KeyEvent.KEYCODE_BACK)) {
        Toast.makeText(getApplicationContext(), "goodbye! (back button pressed)", Toast.LENGTH_LONG).show();
        finish();
        return true;
    }
        return false;
}

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);      

    boolean hasBackKey = KeyCharacterMap.deviceHasKey(KeyEvent.KEYCODE_BACK);
    boolean hasHomeKey = KeyCharacterMap.deviceHasKey(KeyEvent.KEYCODE_HOME);

    if (hasBackKey && hasHomeKey) {
        // no navigation bar
        Toast.makeText(getApplicationContext(), "no nav bar", Toast.LENGTH_LONG).show();
    } else {
        // navigation bar
        Toast.makeText(getApplicationContext(), "nav bar", Toast.LENGTH_LONG).show();
    }
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment())
                .commit();
    }
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.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();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        return rootView;
        }
    }

}

我有一个nexus 5所以它有导航栏，我认为这是问题

我该如何解决问题？

nexus 5，android 4.4.3

感谢

Answer 1

框架永远不会向应用发送KEYCODE_HOME。现在，当用户离开您的应用时（而不是单个活动），您最好的指标就是在onTrimMemory(int)中聆听TRIM_MEMORY_UI_HIDDEN。

public class MainActivity extends Activity {
    public void onTrimMemory(int level) {
        super.onTrimMemory(level);
        if (level == TRIM_MEMORY_UI_HIDDEN) {
            Context ctx = getApplicationContext();
            Toast.makeText(ctx, "gone", Toast.LENGTH_SHORT).show();
        }
    }
}

此外，您不应仅仅因为用户离开而finish()，然后当用户返回活动时，始终必须从头开始重新创建，无需状态。

java - 需要keycode_home的帮助

1 个答案: