如果不想创建自定义工具栏，可以这样做

public class GalleryActivity extends AppCompatActivity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        ...  
        getSupportActionBar().setTitle("Select Image");
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == android.R.id.home) {
            finish();
        }
        return super.onOptionsItemSelected(item);
    }
}                     

在你的AndroidManifest.xml中

<activity
    android:name=".GalleryActivity"
    android:theme="@style/Theme.AppCompat.Light">        
</activity>

你也可以把这个android:theme="@style/ theme . appcompat . "轻"到< application >标签，用于应用于所有活动

我看到了很多答案，但这是我之前没有提到的。它从API 8+工作。

public class DetailActivity extends AppCompatActivity

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

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

    // add back arrow to toolbar
    if (getSupportActionBar() != null){
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // handle arrow click here
    if (item.getItemId() == android.R.id.home) {
        finish(); // close this activity and return to preview activity (if there is any)
    }

    return super.onOptionsItemSelected(item);
}

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    toolbar.setNavigationIcon(R.drawable.back_arrow); // your drawable
    toolbar.setNavigationOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            onBackPressed(); // Implemented by activity
        }
    });

21+ android:navigationIcon

<android.support.v7.widget.Toolbar
    android:navigationIcon="@drawable/back_arrow"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"/>

MyActivity extends AppCompatActivity {

    private Toolbar toolbar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        toolbar = (Toolbar) findViewById(R.id.my_toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        toolbar.setNavigationOnClickListener(arrow -> onBackPressed());
    }

简单和容易的方法显示工具栏上的返回按钮

将此代码粘贴到onCreate方法中

 if (getSupportActionBar() != null){

            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
            getSupportActionBar().setDisplayShowHomeEnabled(true);
        }

将这个覆盖方法粘贴到onCreate方法之外

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if(item.getItemId()== android.R.id.home) {

        finish();
    }
    return super.onOptionsItemSelected(item);
}

效果很好

public class BackButton extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.chat_box);
        Toolbar chatbox_toolbar=(Toolbar)findViewById(R.id.chat_box_toolbar);
        chatbox_toolbar.setTitle("Demo Back Button");
        chatbox_toolbar.setTitleTextColor(getResources().getColor(R.color.white));
        setSupportActionBar(chatbox_toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        chatbox_toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //Define Back Button Function
            }
        });
    }
}