final MyDialog dialog = new MyDialog(this);

        LayoutInflater inflater = getLayoutInflater();

        LinearLayout layout = (LinearLayout)inflater.inflate(R.layout.layout, null);

        CautionTv = (TextView) layout.findViewById(R.id.ion_tv);

        ContentTv = (TextView) layout.findViewById(R.id.ntent_tv);

        LanguageTv = (TextView) layout.findViewById(R.id.guage_tv);

        OkBt = (Button) layout.findViewById(R.id._ok_bt);

        OkBt.setOnClickListener(new OnClickListener() {

            @Override

            public void onClick(View arg0) {

                if (dialog != null) {

                    dialog.cancel();

                }

            }

        });

        dialog.show();

        dialog.setCancelable(false);

        dialog.setContentView(layout);// show方法要在前面

import android.app.Activity;

import android.app.AlertDialog;

import android.content.Context;

import android.os.Bundle;

import android.view.Gravity;

import android.view.WindowManager;

import android.view.ViewGroup.LayoutParams;

import com.android.launcher.R;

/**

 * 自定义弹框

 * @author xiebin

 *

 */

public class MyDialog extends AlertDialog {

    Context mContext;

    public MyDialog(Context context) {

        super(context, R.style.MyDialog); // 自定义全屏style

        this.mContext=context;

    }

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

    }

    @Override

    public void show() {

        super.show();

        /**

         * 设置宽度全屏，要设置在show的后面

         */

        WindowManager.LayoutParams layoutParams = getWindow().getAttributes();

        layoutParams.gravity=Gravity.BOTTOM;

        layoutParams.width= LayoutParams.MATCH_PARENT;

        layoutParams.height= LayoutParams.MATCH_PARENT;

        getWindow().getDecorView().setPadding(, , , );

        getWindow().setAttributes(layoutParams);

    }

}

<!-- 全屏style -->

    <style name="MyDialog" parent="@android:style/Theme.NoTitleBar.Fullscreen">

        <!-- 是否有边框 -->

        <item name="android:windowFrame">@null</item>

        <!--是否在悬浮Activity之上  -->

        <item name="android:windowIsFloating">true</item>

        <!--标题  -->

        <item name="android:windowNoTitle">true</item>

        <!--阴影  -->

        <item name="android:windowIsTranslucent">true</item><!--半透明-->

        <!-- 点外边可以消失  -->

        <item name="android:windowCloseOnTouchOutside">false</item>

    </style>