java – DrawerLayout导航抽屉未显示

我正在尝试在工具栏中显示导航抽屉.我认为我已经编写了所需的一切,但工具栏中没有显示任何内容.只有文字动物园.不是显示导航栏的图标

我是android新手,如果我错过了某些东西,我不会感到惊讶.

这是我的MainActivity.java

package com.example.zoo;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
public class MainActivity extends AppCompatActivity {
    private DrawerLayout mDrawerLayout;
    private ActionBarDrawerToggle mActionBarDrawerToggle;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setHomeButtonEnabled(true);
        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_Layout);
        mActionBarDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout,R.string.drawer_opened,R.string.drawer_closed){
            @Override
            public void onDrawerOpened(View drawerView) {
                super.onDrawerOpened(drawerView);
                if (getSupportActionBar() != null) {
                    getSupportActionBar().setTitle(R.string.drawer_opened);
                }
            }
            @Override
            public void onDrawerClosed(View drawerView) {
                super.onDrawerClosed(drawerView);
                if (getSupportActionBar() != null) {
                    getSupportActionBar().setTitle(R.string.drawer_closed);
                }
            }
        };
        mDrawerLayout.setDrawerListener(mActionBarDrawerToggle);
    }
    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        mActionBarDrawerToggle.syncState();
    }
    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        mActionBarDrawerToggle.onConfigurationChanged(newConfig);
    }
    @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.
        if(mActionBarDrawerToggle.onOptionsItemSelected(item))
            return true;
        int id = item.getItemId();
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

这是我的content_main.xml


当然我有这些字符串名称


最佳答案
问题是这一行：

getSupportActionBar().setDisplayShowHomeEnabled(true);
对于您当前的设置,它应该是：

getSupportActionBar().setDisplayHomeAsUpEnabled(true);
您也可以使用Toggle的五参数构造函数,并将Toolbar对象作为第三个参数传递.

mActionBarDrawerToggle = new ActionBarDrawerToggle(this,toolbar,R.string.drawer_closed) {...};
在这种情况下,您可以省略支持ActionBar set *()调用,并在Toggle上检查onOptionsItemSelected(item).如果您的工具栏未设置为支持ActionBar,这将非常有用.但是,如果工具栏设置如此,则documentation建议使用四参数构造函数,从而推荐当前设置.

java – DrawerLayout导航抽屉未显示

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